One track records to another

This applies to 2.0 and 3.0......

I have a completed mixdown I want to add keyboards to. I have an M-Audio Audiophile card and a midi keyboard connected by midi cable. Using Kontakt 3.0 to access the sounds. I don't want to record the keyboard as midi, just as the actual wave file.  Normally my input settings in Audition are M-Audio Delta AP Multi but in order to have the keyboard come through I have to change that track to M-Audio Delta AP Mon. Mixer. The keyboard records fine but the track also records the mixdown track as well so I don't end up with a separate keyboard track, just a mix of both. Any suggestions?

Thanks.