[macro-outgoing]
exten => s,1,SetCallerID(${OFFICENAME})
exten => s,2,Dial(Zap/1-1/${EXTEN})
exten => s,3,Gotoif(Congestion?4)
exten => s,4,Dial(Zap/1-2/${EXTEN})
exten => s,5,Gotoif(Congestion?6)
exten => s,6,Dial(Zap/1-3/${EXTEN})
exten => s,7,Busy
exten => s,8,Hangup


and it is called from a context like this:

exten => _NXXXXXX,1,Macro(outgoing)