Record from DJM-900NXS2 to Rekordbox No Mic

I use RB to record my mixes which is connected to my DJM-900NXS2 via USB A.

My booth out goes to a different audio interface on a different computer for my live stream.

How can I record the mix on RB without recording the mic from mic input 1? Is this possible without having to get another external mixer?

Thanks