After reading some more, I'm reasonable sure linux permissions will not work this way directly. In this case, I'm guessing my best solution will be to have passworded FTP access, and to provide that to the accounting users. I'm aware that FTP transmits the password "in the clear". The information being accessed isn't of a confidential nature, but we just don't want certain employees having ready access. Anyway, most of them think FTP is a brand of motor oil.

I hope this helps anyone else in my situation.
Dave