Home runs are a matter of simple arithmetic. No one needed a calculator to follow Mark McGwire down the stretch of his record-breaking 1998 season. The home runs just added up. What was gained could never be lost.

What Todd Helton is doing this summer is more complicated. Forget the pennant and wild-card races. The most exciting division in baseball is the computation that goes on after every at bat by Helton, the lefthanded-hitting Colorado Rockies first baseman. He's trying to become the ninth man since 1900 and the first in 59 years to hit .400. The mathematics of that pursuit are as daunting as the history.

"You picked up a point today," a reporter informed Helton after he got two hits in four at bats in Colorado's 11-4 win over the Pittsburgh Pirates last Saturday, raising his average to .393.

"I got a whole point," Helton said in mock excitement. "I'll celebrate tonight."

His droll response was understandable, considering that Helton had entered the series at Three Rivers Stadium last Friday on a 10-game tear in which he'd smashed 15 hits in 39 at bats--and lost a point on his batting average. His 2-for-4 day on Saturday only meant that he would have to put together nine more consecutive games like it just to get to .400. Go figure.

On Sunday, Helton again went 2 for 4 in the Rockies' 9-2 defeat of the Pirates, leaving him at .394. Based on his rate of at bats per game through Sunday, Helton would need to hit .431 the rest of the way (50 for 116 over 32 games) to finish at .401. Then again, he's still at such a preposterously high level that he could go 0 for 116 and finish at .315, his career average entering this season.

Whether Helton hits .400 or not, he already has succeeded in proving how difficult the task is. Ascending to .400 this late in the season is like climbing Mount Everest: the closer to the summit, the more treacherous it is to advance, the easier it is to plummet. "What I've found out is that it is a little bit of a psychological barrier," Helton says. "I try not to stare at the scoreboard when I bat, but hitters usually know what they're hitting."

Through Sunday, Helton hadn't finished a day at .400 since June 10. Yet he was at .390 or better in 28 games since then, including 16 consecutive games at week's end. (The Coors Field scoreboard in Denver had him at .400 after he singled in his first at bat on Aug. 21, but that was only by rounding up from .3995, a practice that baseball's official statistician, the Elias Sports Bureau, doesn't apply for such a milestone.)

"When I don't get a hit now, being this close, it does get a little more discouraging," Helton says. "I hit line drives at the pitcher twice [last week] and was out both times. That hurts. But I knocked in a run with one of them. I also realize I can't guide the ball. I can't pull out a wedge and place the ball over the shortstop's head. All I can do is swing hard and hopefully get a hit."

The eight .400 hitters since 1900--including Ty Cobb and Rogers Hornsby, who each accomplished the feat three times, and George Sisler, who did it twice--are all in the Hall of Fame except Joe Jackson. (He's not eligible for induction because of his ban from baseball related to the fixed 1919 World Series.) No one has hit .400 since Ted Williams batted .406 in '41 for the Boston Red Sox. Thus the milestone has been out of reach longer than were the single-season home run records of Babe Ruth (34 seasons) and Roger Maris (37).

Since 1941 only three players have even finished with an average better than .380: Williams (.388 in '57), the Minnesota Twins' Rod Carew (.388 in '77) and the Kansas City Royals' George Brett (.390 in 1980). The San Diego Padres' Tony Gwynn hit .394 in '94, but that season was truncated on Aug. 11 by a players' strike, making his average the equivalent of ending the Boston Marathon before reaching Heartbreak Hill.

"In a lot of ways Todd reminds me of George Brett," says Colorado manager Buddy Bell, Brett's third-base contemporary during his playing days. "Their passion, their work ethic and their respect for the history of the game are similar. George was the greatest hitter I ever saw, and he couldn't hit .400, so that should tell you something about how hard it is."

As of Sunday, Helton, 27, who had missed only two games all season, already had more at bats (465) than Williams had in 1941 (456) or Brett had in '80 (449). Brett missed nearly a month of that season with an ankle injury and another week in September with tendinitis in his right hand. After a slow start that left him at .255 on May 23, Brett reached .400 for the first time on Aug. 17. He was batting .401 as late as Sept. 4 (chart, left) and .3995 as late as Sept. 19, but a 4-for-28 slump over the next seven games ruined his chances. He batted .324 in September.

"I had as much fun as I possibly could," Brett says, "but all of a sudden, I got close. With a few weeks to go I was still over .400, and I did the one thing I probably shouldn't have done: I tried to hit .400 rather than just go out and not worry about it. When I got close, I tried too hard. I've always said that in baseball, you can't try hard. You have to do everything easy."

When told of Brett's comments last Saturday, Helton said, "I'm glad you told me that, because lately I feel I've been trying to force things. I've been too conscious of getting hits rather than just putting a good swing on the ball. It's reassuring to hear him say that. I know what it feels like."

Williams entered his famous final weekend in 1941 batting .401. "A batting record's no good unless it's made in all the games of the season," Williams said during an off day, one of two straight and nine that month, on Friday, Sept. 26, in Philadelphia. The next day he went 1 for 4 against the Athletics, dropping his average to .3995. Then, in front of 10,268 fans at Shibe Park, he went 4 for 5 and 2 for 3 in a final-day doubleheader. Williams hit .397 in September that year. Mindful of that history, Bell says he may offer Helton the opportunity to take "one or two" days off the rest of the season. Helton, however, vows that he will play every game.

"People have asked me what will happen if Todd's hitting .401 going into the last weekend," says Bell, whose Rockies finish with three games against the Atlanta Braves at Turner Field. (Helton has hit .292 in 24 at bats against Atlanta this season.) "He's going to play, and I believe he would have a better shot at hitting .403 than .399. One thing that makes him great is he has absolutely no fear."

Helton's task is more difficult than Williams's was for several reasons: the evolution of relief pitching ("Todd almost never sees a tired arm and sees a lot of lefthanders late in the game," Bell says); vast improvements in fielding; and a more rigorous schedule. Williams played only two teams outside the Eastern time zone and none farther west than St. Louis. Because of injuries, off days and 15 rainouts, only twice did Williams play more than 10 consecutive days that season--once for 15 days and once for 16. This season the Rockies played 41 games in 42 days before an off day last Thursday, crossing time zones 10 times. On the other hand Helton benefits from advances in training, nutrition, jet transportation and scouting, plus video aides.

Like Williams, who hit .425 at Fenway Park in 1941, Helton enjoys a hitter-friendly home stadium. Coors Field may skew offensive numbers more than any other park in history, with Helton among the many players who have prospered there. Fly balls carry about 10 percent farther at Denver's mile-high altitude than at sea level. In an attempt to compensate for that, Coors has a vast outfield--but that leaves exaggerated spaces in front of and between outfielders, which creates more room for hits to fall. Helton is a career .381 hitter at Coors but .291 elsewhere. This season he had hit .425 at home and .362 on the road.

Colorado was scheduled to play 19 of its final 29 games at home; included are visits this week from the pitching staffs of the Milwaukee Brewers (4.67 team ERA) and Chicago Cubs (5.04). Helton was hitting .423 against the Brewers this season but a mere .091 against the Cubs. "All he has to do is keep his head above water on the road, and he can do it," says Jim Leyland, who managed the Rockies last year. "When he gets home, especially against mediocre pitching, it's easy to get three hits a night there. I think he's going to do it."

"Gee, thanks," Helton said, rolling his eyes at Leyland's comments. Helton, like most Rockies hitters, doesn't like to acknowledge the Coors advantage. "Is it a good park to hit in? Yeah," he concedes. "So are Wrigley Field and Camden Yards. I didn't design Coors Field; I just play there. But if I had designed it, I'd be proud of it. It's a beautiful place to play."

"This is what I've told Todd," says Colorado hitting coach Clint Hurdle, who was a teammate of Brett's in 1980. "There's nothing negative about what you're doing. Todd's real sharp. He's learned so much quicker than most people to worry only about what you can control. Everything else, you let go."

Helton has improved in each of his three full seasons in the big leagues. With a slope-shouldered physique reminiscent of those of Stan Musial and Don Mattingly, Helton is an all-fields hitter with power who walks often and rarely strikes out. Through Sunday only seven batters in baseball who could qualify for the hitting lead--none of whom had more than 12 home runs--had been tougher to fan than Helton, who had 32 dingers while whiffing only once every 13.0 plate appearances. He had failed to make contact on only 9% of the pitches he had swung at this season. "It's like he's got radar in his bat," says Colorado reliever Gabe White, who joined the Rockies in April after a trade from the Cincinnati Reds. "He can swing at pitches that are real pitcher's pitches and still get the bat on the ball. He can foul it off and get to the pitch that he really wants to hit. He can hit .400. If he's done it this late into the season, he can do it."

Helton, too, has begun to believe. Until the series in Pittsburgh, he had dismissed talk of hitting .400 as "too early." Then before last Saturday's game, Helton was close enough to the summit to say blankly, "I think it can be done."

The .400 watch is beginning to build. Last Friday the Rockies arranged a news conference with Helton in the visitors' dugout at Three Rivers Stadium. Eight media members showed up, about 25 fewer than attended a press gathering for McGwire in the same stadium at a similar juncture in the 1998 season. Helton stood and answered questions politely but with the bored, glazed look of someone shaving. The press is in the process of discovering him.

"Can you sing Rocky Top?" one reporter asked Helton, a former University of Tennessee quarterback, referring to the Volunteers' fight song.

"I can but I won't," Helton retorted.

Later, after the group had dispersed, Helton said of the growing scrutiny, "It's August, and there's a lot of time left. I never thought I'd be doing this, so who knows what's going to happen? If I don't do it, it won't be because I was distracted."

Helton already has carried the chase longer than anybody else in 20 years. That alone says much about him and .400. "There's a reason nobody's done it since 1941," says Bell.

Hitting .400? It's hard as Helton.