How do I tell if accounting module fails?

Hi all, I'm using an Exec-Program to do some user-specific stuff when a user logs out of our network (i.e. it is invoked with "DEFAULT Acct-Status-Type == Stop"). I'm trying to find a way for it to detect whether the database accounting module has succeedded in updating the user's accounting record or not (it will fail if the STOP packet is a duplicate). I can't find an attribute that I can test to check the status of the request at that stage. Any suggestions? Alex