Add people to a secondary group for a certain time period

[joshpet]

I'm looking for something, even a paid plugin is good - I just haven't found what I'm looking for.

I'd like to be able to add someone to a secondary group for special access for a pre-determined period (30 days, a year or whatever I want).   

Is there such a way and/or plugin to do that?   Willing to pay to develop if someone can do it.