Yes this should work quite fine. Just make sure that the output from the mixer is NOT an amplified signal.
I would use a couple of AUX's from the mixer and send those into the AudioBox
If the mixer doesn't have aux's, you should be able to use something like tape send
Just as a precaution, I would make sure that the phantom power is NOT on, on both devices
as I have had bad experiences when it has been on on both devices at the same times)