Not quite - browsing thru this thread, we seem to have already got to the stage where user ID and/or computer is checked...

Now, we've established they're working from home, so - now ask for their authorization password to establish that they're allowed to work from home.

You could have a number of passwords, including time-limited ones that allow access for one hour, day, week (whatever) and maybe unlimited ones for the really trusted employees. (The temp passwords could also be changed regularly if you think they're being passed around )