I would think it should work, but I would want to check the technical specs of each microphone to make sure they are somewhat compatible. You don't want to saturate the mic input.

The more I think about it the more I think it should work as all the measurements being taken are relative and the microphone should cancel itself out.

You could always try it and not commit the results if they look like garbage. I take it that you have a pretty good idea what the results should be for your setup already? I don't think there's much risk of physically damaging the mic input of the 990.