can someone help me get headphone cue working please

hi every one  i cant seem to  get  headphone  cue/mixer working  iv looked in midi settings  but  cant seem to asssign each  deck ...only  time i  can here  1 or the  other  is if i  have  both  cue buttons on ...and  would  like it  so i  only have 1 cue  on  and use  headphone mixer on   

PLEASE SOME HELP :(   i cant seem to  do it  for the  life of me