Using External Monitor. Want Mouse to move Up/Down, not Left/Right? I've got an external monitor and want to be able to use the monitor above the laptop. 

It seems I'm supposed to use "Spaces" to support an external monitor which I have done and I've set up two spaces for this. Unfortunately it seems that I'm only able to move between spaces by moving my mouse cursor from left to right instead of from top to bottom and vice versa. Given the layout of the monitors it is really unnatural to have to move from left to right in order to access monitors that are stacked.  I can easily do this on my Dell laptop running Windows but is there a way to do it with my Mac's OS X?  Stumped.


(source: mikeschinkel.com)  

Thanks in advance for the help.

-Mike
You don't need to worry about Spaces for this.  What you need to do is go into:

System Preferences --> Displays --> Arrangement

Drag the icon representing your external monitor to the top of the icon representing your macbook monitor:



You can also drag the bar representing your menubar/dock to whichever monitor you want to be your "main" display.