Ways to control mouse/keyboard of 4 computers at the same time (all 4 mouses move as one?)

I'm trying to find either software or hardware that will allow me to control 4 computers at the same time from 1 keyboard and mouse. When i say control all 4 at the same time, i mean if i move the mouse then the mouse cursor will move on all 4 pcs at the same time. I've tried things like synergy but that only moves the mouse between the screens, it doesn't do what i want atall.

Is there any software or hardware that can do this? It's for multiboxing in Diablo 3.

http://www.dual-boxing.com/threads/4...ing-Diablo-III

I think he have enough threads on multiboxing Diablo III.