Kind of ghetto, but... [dial]
> exten => s,1,Answer()
> exten => s,n,Playback(welcome-msg)
> exten => s,n,PlayTones(dial)
> exten => s,n,Set(TIMEOUT(digit)=5)
> exten => s,n,WaitExten(60)
exten => _X,1,StopPlaytones()
exten => _X,2,SetVar(NR=${EXTEN})
exten => _X,3,Goto(dial2,s,1)
[dial2]
exten => s,1,WaitExten(60)
exten => _X.,1,Dial(SIP/provider/${NR}${EXTEN})
