22ce33a2_dj_control_mp3_e2__Mixxx_Wiki___Function
[Control] Cue [number] 15 [Function] 
Sets the cue point if a track is stopped and not at the current cue point. Stops track and returns to the current cue point if a track is playing. Plays preview if a track is stopped at the cue point for as long as it's held down
hercules_dj_control_mp3_e2 [Mixxx Wiki]
Function