Change "Multiple Displays" combo box in "Screen Resolution" panel

Question

What I want to do is to select "show desktop only on 1" or "show desktop only on 2" (if you have 2 monitor) via code.

I've read about how to change resolution, orientation and how to make a monitor the predef. but i haven't read about this.

How to do that? There is a method like -Change display settings- that could help me?

I was wondering if there is a registry key with the combo box value saved, so i can edit it by code.