It can't be done within the machine so export the track, copy the file from AudioDepot to a computer and import to your DAW (the free Audacity has a reverse function). Reverse the track, either just selected sections or the whole thing. Export the reversed track from the DAW to a wave file, ensuring the format is unchanged (bit rate & sampling freq), copy to the DP24's AudioDepot folder and import it to a spare track in your song.