Mine

exten => 18478971337,1,Macro(stdexten,${MATT},20,,100)


[macro-stdexten]
; ARG1 = Device to Dial
; ARG2 = Timeout
; ARG3 = Dial Options
; ARG4 = Voicemail box to use.  NONE if no VM.

exten => s,1,Dial(${ARG1},${ARG2},${ARG3})
exten => s,2,GotoIf($["${ARG4}" != "NONE"]?s-${DIALSTATUS},1)
exten => s,3,Hangup

exten => s-NOANSWER,1,Voicemail(${ARG4},u)
exten => s-NOANSWER,2,Hangup

exten => s-BUSY,1,Voicemail(${ARG4},b)
exten => s-BUSY,2,Hangup

exten => _s-.,1,Goto(s-NOANSWER,1)