Well, if you want to get technical you could write a script to do it, then put it in your dock, or set it to open at login or just launch it whenever you need it, or you could even set it as an iCal event to turn on and off at certain times.
Or, you could create a script, and then save it as an application using automator. Then, you can assign an application shortcut for the keyboard.
long and complicated, but it gets the job done...
http://docs.info.apple.com/article.html?path=Mac/10.5/en/8564.html