Master- Monitor/Headphone issue

Hy everybody. I buyed this Gemini Firstmix i/O controller a few months ago. My problem is that i can't figure how to prelisten track in the headphone withouth hear it in the Master. i already googled every answer and forums but nothing helped me.Now if i use some other software like Traktor i can set the prelistening as it should and I don't know whi this is not possible with Cross DJ? i thing it need a new mapping for the buttons. So please anybody help me?