Help with unknown protocal assignment - UDP ports

I am trying to assign traffic types with unknown ports, I can get it to assign the port but I am running into a problem with UDP ports.

I have alot of VoIP traffic which of course picks a random UDP port in a range say from port 20000 to 45000. The problem is if I assign it to the SIP group I create any traffic that uses any of that range with be classified as SIP traffic when it is not.

Since many applications pick UDP ports at random can you give me any suggestions on the best way to correct this?

I have certain IP's that only have SIP traffic on certain UDP port ranges but I do not see a way to tell the software that traffic from a certain IP using certain ports is SIP and not show it as VoIP traffic for other IPs.