Network Throughput Detection (c#)

Question

Hi All,
I'm writing some code that suppose to send UDP packets from one of the available network interfaces.
The logic I want to use is to send from the less "busy" interface.
I'm trying to figure out a way to monitor the outgoing throughput without using the perfrmance counters since finding out the IP to bind from the performance counter instance is not simple (if possible at all).
I can track what I send but I need to assume that other processes can send what ever they like.
Any idea?
Thanks!