Banning by Name

Is this possible

[Visi]

I have an unwanted visitor, eating up my site. Have domain name user is from but not IP. Is it possible to ban by name rather than IP?

Thanks

[Visi]

Found it in an old post, isn't the search function just wonderful. Hangs head in shame....apologizes to all...blushes ....and crwals back under his rock:)