Thanks to everyone for the great help.
It sounds like I need to upgrade to a better version of Sonar.

Tim

Hello all, 
I may be doing this wrong, because the suggestion above didn't work for me.
I have a compressor routed as such via my Focusrite Saffire Pro 40:
Saffire outputs 5/6 > Compressor inputs 1/2 > Saffire inputs 5/6
I created the bus as described by tlw, but got no audio coming back, but the meters on the track in Sonar moved.
So, I have a stereo drum track output set to Master and the input on my processed track set to input Stereo 5. BUT that required me to solo the drum track so the compressor only compressed that track, not the whole mix.
This seemed to work, but doesn't seem right to me, especially after tlw's directions.
I should be able to send the drums out to the compressor (output 7/8) and record compressed drums on a new track from the compressor (input 5/6), with or without a bus.  right???
 
Thanks
Tim