Originally Posted by Chuckoir

Buuuut, if you go into preferences and then select "Mouse", there may be a section in there which shows which gestures you can use?

Failing that, you could download a brilliant little app called "BetterTouchTool", which will allow you to assign addition gestures to the Magic Mouse.

Or, if that's not to your liking, you'll have to just press "ctrl + left arrow" or "ctrl + right arrow" to switch between.

Link to BetterTouchTool: BetterTouchTool (Mac) - Download