Mixture and Prop Control

OK chaps/chapesses can anyone help with this. I have a Saitek X52 Pro Joystick, when you move the throttle control when flying a twin or four engined plane all the throttle controls move together. But when using the joystick to adjust mixture or prop controls only one moves, I usually use the slider on the Saitek to control mixture on a single engined machine. So is there any way to tie these controls to operate with one assignment on the joystick. I.E. the slider control would control all mixture adjustments.
Sorry it's a bit long-winded but I have problems writing what I'm thinking
Cheers
Rich


Cheers
Rich