Override mouse coordinates?

I have an unusual situation. I am using a 2 monitor setup with a touchscreen, where the touchscreen coordinates do not line up with the screen. I can fix it with some simple math, but is there a way to override the built-in mouse events, so that buttons and controls behave correctly? The only change I have to make is to halve the x coordinate.

There is no way to do this transparently, but you could implement a property that does the halving for you whenever you access it.