provide an example of max membership in group

Lauren Burkhardt: We're looking at trying to set a limit on how far out someone can set an expiration date for a user's membership in a group. For instance, we only want people to be a member of a group for up to a year. Is there any way to enforce that if a user is added to a group, that the end date for their membership can't be more than a year in advance? Has anyone done something like this? I have not been able to find anything in the Wiki