mysql account and users account using exec-program-wait

I store all user account in mysql, and freeradius works fine. And now, we have some special account that need to write a external program to do authentication. So we use the users file using DEFAULT auth-type = Accept with exec-program-wait. The problem is all mysql accounts doesn't work any more. We check with radiusd -X and find all mysql accounts will pass to users and run exec-program-wait. I just want to know how can we stop the users checking if mysql return OK. Regards, Santa Yeh