Keyboard shortcut...how do I do this...?

I need to be able to switch between the internal speakers on my iMac and the external speakers that I have connected through a FireWire device.

Is there any way to set a shortcut to change the Audio Output setting just by clicking one button? (i.e. hit F8 or whatever once, and it sets output to the firewire device setting, hit it again and it goes back to internal speaker setting)?

Thank you!

Anyone?

I'd like to set one up too but have given up.
Still stuck with System prefs > Sound > Internal or Altec Lansing