V 2.0 of Cool Edit Pro? If so, just go to your multi track view. You can arm each track for recording with the little red button next to the track labeled with an "R". Insert your recorded track into track 1. Be sure that track 1 isn't armed for recording or you will record over your track. Then arm track 2 to record. Press your record button and off you go. Track 1 will play as normal and track 2 will record.