A critical question about COM+ and Callback functions

Hello guys.

I need to call an asynchronous process within a COM+ server: while the method is running, the user must be notified about the processing progress.

Well, I tried to use Events (raiseevents), but with no success... So I tried to use callback functions (I read that this is the right way to to interact with the client application), but with no success again...

Does anyone know how can I notify my client application about the processing progress?

Thanks in advance,
Piazza