Expanding queues



I’m currently setting up an Asterisk server for a small office. Now if there’s an incoming call we want a few phones to start ringing. If these phones don’t answer the call, some more phones should start ringing as well. Then if the call still isn’t answered, all phones should start ringing. First I tried to implement this using 3 queues which are tried after each after, with each queue containing more members. However, this has one disadvantage in that everytime a queue is left to enter the next queue, it counts as a missed call for the phones that were ringing. So if a call isn’t answered after all three queues were tried, the phones that started ringing first show 3 missed calls in their display and the phones that started ringing from the second queue report 2 missed calls. This also has the disadvantage that if a call is answered when in the second queue, the first phones still report a missed call.
Does anyone know of a way to achieve this without interrupting the dial command for the earlier phones when moving to the next queue?

Thanks in advance,

Arend jr.