Yes. Although it wouldn't be a bot, there's a funny name for it. Not a proxy.. I can't remember what it's called. But yeah, tell the game to connect to 127.0.0.1 instead of Battle.net, and your program listens on Battle.net and forwards the packets to the Battle.net server and from the Battle.net srever back to the game.
When I did that, however, I couldn't use UDP because VB sucks at UDP. In other languages, it would probably be possible, though.