Asterisk: keep a caller on hold, start new call, and conditionally transfer ?

Hello,


I'm using asterisk for my land lines, and when I am not picking up my SIP phone after couple of rings, I try to dial a cell phone, then if i'm not answering that either, i try another number, and so on.
The problem is when a cell phone is turned off or out of range, it picks up immediately with the voicemail (no rings), and asterisk thinks the line has been picked up and transfers the call.

exten => 123546,Dial(Zap/g1/15554443333)

What I'm trying to do, is when the line is picked up, to play a message saying "press 1 to accept the call", and if the DTMF 1 is not pressed within a short timeframe, then the call is hangup and the next cell phone on the list is dialled.

The "Dial" command is automatically transferring the caller when the line at the other end is answered... How do you keep the original caller on hold, while playing the menu option to the person dialled-out ?

Thanks so much !!