need help with sketchup on os x

[bimmerboii]

Anyone here uses Sketchup on mac? I have this annoying problem.. Since I used to ba a windows user, I can easily 'orbit' or rotate my drawing when pressing the middle mouse button. Now in my new mac, pressing the middle mouse button opens the expose (not sure what its called). Any way to use the middle mouse so that it properly rotates my drawing on my mac?

 

[bimmerboii]

its not dashboard that comes up, it opens all windows as thumbnails. I have done what u said above and set removed dashboard and expose buttons but it still does it..

 

[bimmerboii]

if you can see my screenshot i already removed the assigned button for expose but it still does it. im confused

edit: when i rebooted my mac everything seems to be ok now. problem is when i press the middle mouse button it still wont orbit in sketchup. it only does nothing. any way i can bind keys in sketchup?