I'm looking for a birthday-related addon to CB. But NOT one that shows users with upcoming birthdays on the front end.

I'm working on a site for a local business, and they'd like to offer their customers a special during the month or week of their birthday. Right now, I have it set up so that users enter their birthday when registering, but I can't find any way to actually use that data.

Ideally I'd like some way to add users automatically to a filtered group so that they can access their birthday "special" only during the specified time. Like a "birthday" usergroup, with the special page being only visible to those within the usergroup.

At the very least, I'd like to be able to sort users by their birthday from the back-end, so that we can manually add them to the "birthday" usergroup for the specified time.

I don't suppose there's anything out there even remotely similar to this, is there?

Any help/suggestions would be most appreciated! Even if it ends up not being a CB solution (we're only using CB for the easily-editable registration page anyway...there isn't much social interaction taking place on the site).