asterisk users - Jun 2006 - Limiting the size of a Queue

Is there a way to limit the size of a Queue? I want to create a queue 
with for example, 5 agents, and only allow at most 10 persons waiting
so this way, they don't saturate my entire PSTN span, which can be
also simultaneously used for another Queues or for my outgoing calls.

Thanks a lot for your attention.

-- 
Atly.
Alvaro Palma