When in fullscreen stop mouse from moving to extended desktop

Hi all,

I play a game called starcraft 2, when playing this game you drag the mouse off the right side of the screen in order to move right. I just setup an extended desktop with one screen to the right of the primary.

When playing this game and trying to move right the mouse just moves onto the extended screen. Is there a way to stop this happening so when I am running the game to lock the mouse into it so that it wont move across to the other screen (so I'd have to alt + tab the game to do so).

It is really annoying and means I cannot play at all, so I would REALLY apreciate any help that people can offer!

Thank You