Feature to report multiple user names using same IP address?

[caldangel]

I have someone on my site who is using multiple names and one IP address.

I was wondering if there was a way to have a report sent to an Admin only forum of all users who log in with a shared IP address.

For instance, if user 1 logs in under an IP address and sometime later, user 2 uses that same IP to log in, there would be a post sent out to a pre-established board showing that these 2 users are using the same IP address. Nothing else happens but the posting.

Is there a modification for this?

Thank you.