recording scratches without recording the playback

Hey guys, after endless hours of torturing my brain I hope this forum will finally solve my problem. It should be easy but I just cannot find a way. I have a DJM S9 and I want to record scratches using timecode vinyl with a laptop running serato. I would like to listen to the playback and my scratches on headphones while I am recording. But I only want the scratches to be recorded. What should I do? I tried to route the signal to ableton in order to record both decks seperately, but it will record the timecode audio signal (sine wave). If I record in Serato itself it will record not only the scratches but also the playback, not matter if I play the playback from serato or from another device using the aux or line in from the djm s9. Can I route the djm s9 outputs in the pioneer djm s9 software maybe? Thanks for your help, J