I don't need any keyboard interaction really. Just keep the mouse on the lower half of the scrren and thats it.

I hear what you are saying shock but it would be easier I would think to just prevent the mouse from moving down to the bottom rather than replicating it - mostly due to the added complexity and the mouselook needs to match, which it would automatically if they all have the same freq mouse attached - as long as the mouse was "resycned" such that the top left was caged and prevented from moving to the top of the actual monitor but instead stayed at the top of the game window (even though there was more desktop above it).