You could calculate the number in Perl with (n + 1) % 1000. You would also need to perform a conditional check to see if the row exists or not (difference between insert and update).

Another approach would be to prune out the old users on some kind of regular basis: maybe set up a trigger so that when the magic number is hit, a stored procedure that does the pruning is called.

Just some thoughts :)

Jeff

R-R-R--R-R-R--R-R-R--R-R-R--R-R-R--
L-L--L-L--L-L--L-L--L-L--L-L--L-L--