> SELECT * FROM COSTCATEGORYDEFINITIONS
> WHERE COSTCATEGORYNO = NEW.COSTCATEGORYNO;

What is this supposed to do in a trigger? Looks like Delphi would say
"This code has no effect" - so probably Interbase considers it illegal?

What you could use is a FOR SELECT stament, or an UPDATE statement etc.,
but I can't see what a simple SELECT could be supposed to do.

Cheers,
Tobias