Detect if mouse moves in a direction while there is no cursor (Invisible and LockCenter)?

I need to be able to detect if the player moves there mouse in a certain direction(X+, X-, Y+, Y-), but I also need it to where there is no cursor (Invisible and LockCenter). Is there a way I can detect motion, but not position? Any help is appreciated! I'm sorry I didn't include a script or anything, but basically I am going to have a camera scripted similar to the original, but you do not right click to rotate it, you just move the mouse, and right click zooms in the camera to shoulder view, then the character's rotation follows the camera's rotation.