Headphone trouble with Cross DJ 1.2.9

I just got the mixvibe Cross DJ 1.2.9 and I have a problem with the headphones and sound. everytime I hit the headhone the speakers get louder, How can I separate the two before it goes out to the main sound or speakers?
I have a Mac OS X 10.5.8
and I recently bought a USB X-FI sound card cause I think i might need it to have dual outputs.
Pleae if anybody can give me some information as how to separate the headphoes with the speakers.
Thank You
I have a Mac OS X 10.5.8
and I recently bought a USB X-FI sound card cause I think i might need it to have dual outputs.
Pleae if anybody can give me some information as how to separate the headphoes with the speakers.
Thank You