Sorry, never used Alt-Desk so I don't know how it works, but it doesn't seem possible. Perhaps if you can make a shortcut to bring up alt-desk, you can make an object to activate the shortcut. Alternatively, if you could make your own script file, like .js or .vbs, you could link to them in DX. But I don't have nearly enough scripting knowledge to know if it's even possible to make in DX itself. You may want to email Martin, he's the authority on DXScript, he might be able to tell you if it's possible and how you would go about doing it. I believe his email is Martin@stardock.com
Sorry I couldn't be more of a help...