Можно. Примерно так:
exten => s,1,NoOp()
same => n,Read(pin,please-enter-pin,,,,10)
same => n,GotoIf($["${pin}"="1234"]?ok)
same => n,Playback(invalid-pin)
same => n,Hangup()
same => n(ok),Playback(establishing-connection)
same => n,Dial(SIP/12345678)
