USB mixer recording audio a track at a time

Having spent ages looking I need help here if possible. Just upgraded to Cubase AI8 and have a Peavey 32FX mixer running audio in and out to the PC with no problem at all.

I know the mixer will only record a stereo out at any one time which is fine as this is how I want to build a song

The problem is that after recording audio on track 1 and then adding track 2, because the computer is sending and receiving audio at the same time - track 2 adds my new material as I record it but is also recording the 1st track to itself

You can see that after several tracks this makes mixing impossible as all audio tracks end up on the last track recorded

Can someone tell me how to use cubase to record the new material going through the mixer but NOT adding previous material though still obviously being able to monitor previous audio tracks recorded

Thanks to anyone who can help me to achieve this