Ive been looking into this for the past couple days, I havent tested this solution but it should work.
I have my firewire connected from my mac, routing to aux 4 on the mixer.
now connect a patch cable from aux 4 out, to channel 5 line in. (just an example)
now take aux 4 off of the main and send it to an unused sub.
now both mic and track should be able to be recorded on the computer.
If you try this before me, let me know.