You can do it very easily. In N-track go to File>Settings>Preferences>Audio devices and select which output channel you want to use. While you're there, select which input channel you will be recording to as well. Then patch that output to your outboard unit and patch the output from you unit into the input channel you selected in your Delta 1010lt. Now open your M-Audio mixer and go to the patch panel and make sure that output channel is patched correctly and in the mixer make sure you are reading an input in the correct input channel. Depending on whether or not your MC2 adds gain to it's signal you may have to attenuate the output to avoid clipping. Oh yeah, you still need to solo that track.
Also, you may need to shift the effected track once recorded, as this will usually cause a small delay.
Blessings, Terry