Recording WAVE from other program

Trying to figure this one out. Appreciate any ideas: what do you think the signal chain would look like to have ntrack record audio from another program as well as from an audio interface simultaneously?
I have some loops from Acid going that I am playing over live going into a mackie mixer, then out to LR in of a MIA 2x2 interface. The WAVE in signal of ntrack will pick up what is coming into the interface just fine, but I am looking to be able to do a live recording somehow with ntrack but just can’t it to find the audio from the soundcard from Acid. Do you think this should be possible? Total feedback of course if I try to take the sound card out into an instrument in of the mixer and then back into the audio interface.
Thanks for any suggestions. Hope this makes sense.
SB

I wonder if it would not work better to record the loops on their own tracks, and record the live work to additional tracks.