Install xbindkeys:

sudo apt-get install xbindkeys xbindkeys-config

Get this python script:

• aticonfig_switch.py

and place it e.g. in ~/bin

Make it executable:

chmod +x aticonfig_switch.py

Now run:

xbindkeys-config

and bind the script to a key kombination. I use Winkey+S.

The next time you resume after having docked or resuming in the dock you just wait to the login dialog comes up (the one you cannot see ), type in the password and press the key kombination. You should now get the screen to your monitor after a couple of seconds.

Source: http://cpbotha.net