I have to same problem in http://superuser.com/questions/73921/assigning-programs-to-specific-audio-outputs-in-windows-7 . one of the answer suggested to use virtual audio cable. I have downloaded the trial version but i have totally no ideas how to assign programs to specific audio outputs.
I did a quick search for a tutorial and this one at YouTube might help.
If that doesn't help, can you explain what you are trying to do and what doesn't work?