Since you can read the mouse x and y but not change them, what method can you to change them?
There is no way to actually set the position of the players mouse.
The only thing I can think of that you may or may not actually mean is:
1)Setting mouse as Locked in the center
2)if you actually want to check the mouse position there are ways to do this:
a)Mouse.Target:
if mouse.Target = workspace.Part then end
b)Mouse.Hit:
Mouse.Hit.p Mouse.Hit.X Mouse.Hit.X.p Mouse.Hit.Y Mouse.Hit.Y.p Mouse.Hit.Z Mouse.Hit.Z.p