Terminal Services

We have a remote office that is not part of our domain.

They have 5 PC’s that connect to us using TS.

Right now they just use a general account to login to us, but I want to change it so they have there own Domain Username’s and passwords.

The problem is, I do not want them to login to TS from home or anywhere else, except from the remote office.

Is there a way I can accomplish this even though they are not part of our local domain?

We do not wish to land a DC there at this time.