Trunks queue


I have a system wich forward incomming calls to different cell phones trougth 1 gsm gateway.

What I need to do:

If an incomming call is forwarded, then the second incomming call can’t be forwarded because the trunk is being used, so I would like to put the second call into a kind of queue to wait until the channel is available.

Is that possible?

Thanks in advace