Mc to follow mouse on x axis

Hello
Could someone point me in the right direction with this navigation I want to make.
I have searched and see how to make something follow the mouse but I need to do a bit more.

I want the mc to move accross x axis following the mouse and to centre on button when mouse is within a defined area.
The mc will only follow the mouse when the mouse is near the navigation area.
The fla explains it…I hope

Cheers
Brownie