//Edit - I just saw in your signature that you're using OSX. I highly recommend ControllerMate...
There may be a better official response, but I'd like to suggest a workaround, if you were using Windows:
Go get AutoHotkey for free at autohotkey.com. Run it and "edit the script."
To use the 'caps lock' key to simulate the simultaneous pressing of the 'control' and 'alt' keys, you would add the following two lines to the script:
Code: Select all
*Capslock::Send {Control Down}{Alt Down}
*Capslock Up::Send {Control Up}{Alt Up}
If you're using OSX, you can do something similar with ControllerMate (
http://www.orderedbytes.com/controllermate/) which is excellent but not free ($25).
-David