Blauplunct cd player need a fader from 2 t0 4 speeker

[aiewd]

Hi All, I purchased a Factory fitted Blauplunct 6 in dash stacker cd player to replace my single player in a Australian Holden VY Commodore. The trouble being the 6 stacker came out of a utility with front speakers only. I am putting the unit in a sedan with front and rear speakers, it however does not have a fader. Can this be changed to accomodate the 4 speaker set up.
Regards Aiewd