port forwarding ?

Hey all..getting our audio problems sorted out. This from
the MS help section.

The actual Real-time Transport Protocol (RTP) streams are
sent using dynamically allocated UDP ports in the range
of 5004 - 65535. Without a way to open these UDP ports on
any firewall in the path dynamically, the streams will
fail to reach their destination.

Is there any way of knowing what port is in actual use?

DC