>Do I have to modify all records? I have so far 1000 records already of that format :(

You better do that now, while you have only 1000.

use yourtable
set order to 0
replace yourkey with left(yourkey,2)+transform(val(subs(yourkey,3)), "@L 999") all

And make sure new keys added are made this way. You can actually do this same thing in the lostfocus of the textbox (if any user is entering these), or simply change the logic of your function that creates them to make them this way.