>thanks for reply.
>your suggestion is very nice. but i wanted in different way. warning should come immediately as soons as event occurs. I have just written about this in my previous reply to Don. could you please read it and may be you can help me ? i also want to know that what my customer is needed is acutally possible or not ?

If you want to do it within the same client application then, basically, you should use timer. Another way is to have separate small application running on server which will check for customer credit values and broadcast network messages to all listed users, or even send emails to them.