Well the way I THINK it works is that Mac's kernel differentiates between the two button click differences? I'm not an avid mac user so I really have no clue, but if you're using a Mac mouse I think it is just a single button mouse (read right click only), and not a two button mouse. (which can "left" click and "right" click).
So assuming this is correct, I think you'd either have to change how BT4 recognizes the mouse( I think, I'm not really sure if there's a solution for it). But I do believe you should be able to force the mouse to be a second button mouse, and just switch the settings.
It's there somewhere, no clue as I'm on a different computer. You might wanna try Mouse preferences (I think it's under System). Good luck though