Question : Make specified applications use specified Network Connections on the machine.

I am at a customer site, who of course has a seriously intense internet connection, which of course is all kinds of limited in terms of what I am able to access.

I do most of my communicating with my outside resources via AIM/MSN/Y!, etc - so I need a way to tunnel pidgin through a dial up networking connection that I have available via my tmobile phone.

Answer : Make specified applications use specified Network Connections on the machine.

I am quite certain your network admin can provide you with the necessary information to make the connection, assuming it is acceptable. Back doors are the biggest concern of any network admins job. I recently saw a hospital have to shut down all but essential services for 14 hours due to a similar configuration.

Regardless it is not much help. As mentioned you cannot set MSN as an example to always use one connection.  MSN uses hundreds of IP's in dozens of subnets. You could conceivably choose one of their IP's to be routed through the TMobile connection, but every time you wanted to connect you would have to go to a DOS prompt, retrieve the current IP, and then enter a manual route. I don't know how stable  that would be or even if it would work as big companies do some "fancy footwork" with load balancing across their collection of IP's.