Password protect when *leaving* a desktop

[subpariq]

Curious to know if the idea has been floated or considered to create a way to password protect leaving a desktop. This would allow me to allow others to use *one* desktop, while leaving my current desktops unavailable. While I could hide the method of moving to other desktops, I'd rather not chance them accidentally changing. (And no, I'd rather not the trouble of multiple logins on this particular machine.)

Joey