Store data for alot of records

[I_love_php]

Here is the problem
I create an prediction system for NBA games the idea is any of my users

can come and predcit for the game (who will win and what is the scores
) and everytime one of my admins come and add the score the system
calculate the points users get and store them in the database
here is how my database look like
Table 1 (users) ---- in this table there is User ID and user name
Table 2 is the matchs .... Matchs ID and Team 1 .. Team 2 and the score

Table 3 is Prediction ... it have MAtchs ID .. User ID .. Prediction
score ... and points
now i have around 2000 users come and predict and sometimes when i add
one score it calculate and update for 2000 users for each game so if i
store te score for 10 matchs at the same time it will calculate the
points 20 000 Times and update 20000 records
it took few more sec to do this
the avoid the slow in the future is there any ideas to do this fastest
way ?
im waitting for suggests