If you follow just one racer,you'll see what you want to do is impossible. If racer 1 is in a heat against 2, 3, & 4 and is against 5, 6, 7 in the 2nd heat, havn't 2, 3, 4 already raced against each other? Haven't 5, 6, 7 also met in the previous round?
The only way it could work is for you to ignore the other two racers on the track. If 1 was racing 2 and 3 was racing 4, ignore all results except how 1 and 2 finished by themselves and 3 & 4 by themselves; i.e., you care if 1 finished ahead of 2 (or vice versa) but not against 3 or 4 at that time. Perhaps only have two racers on the track at one time and use standard RR tables on this website.