Hi edstar221,
Try
http://jackosx.com/. It lets you send audio between programs like Logic, MainStage, etc.
The “jackpilot” program has a user interface for connecting virtual audio cables between the apps. It looks a bit ugly and might take a little while to figure out but you can save a preset and load it again in the future.
I run the following chain:
System input -> MainStage -> Garageband -> jammr -> System output
Remember that you need to press “Start” in jackpilot and then go to Logic, jammr, etc to select the JACK virtual soundcard. That means Logic and jammr shouldn't use the real soundcard, they should use the JACK soundcard.
Stefan