asterisk users - Jul 2006 - Asterisk internal extensions caller ID

I trying to find a way of using two different callerid numbers. I have the
callerid="Agent 1" <33xxxxxxxxx> (in the sip.conf) being the
direct dial
phone number, but for internal calls I would like it to show the extension
number. My internal dialplan is.


exten => 3002,1,Set(CALLERID(NUM)=xxx)
exten => 3002,2,Macro(stdexten,3002,SIP/3002)

I know the ${EXTEN} gives me the called extension I'm dialing, but is there
another for the extension that is making the call?

Hope that makes sense.

Thanks,
Dean.