asterisk users - Oct 2004 - how to detect a busy line using analog ports TDM04B (station ports) and using outgoing spool to start the call

All

I am using the outgoing spool to start the call then run my AGI once
the call is placed. All that works.

The problem I notices was that if the number I am calling is busy
I dont get any notification about that. I can sort of understand the
line cant tell me when the user picked up but how do I tell
if the line is busy when starting the call from outgoing spool
call file.

Thanks,

Jerry