This seems to work (where you have field one with the letters to check, and field 2 is the letters that might end with those check letters): on mouseUp put fld 1 into f1 put fld 2 into f2 put offset(f1,f2) into offamount if offamount = the number of chars in f2 - the number of chars in f1 + 1 then put char 1 to offamount - 1 of f2 into fld 2 end if end mouseUp