The ONLY way you can do this is to connect to Open Battle.net, though keep in mind you will only be able to play games with other people that are also on Open Battle.net.
It is impossible to bring a character on Single Player to Closed Battle.net. If it were possible, then the new Ladder would instantly be flooded with hundreds of level 99 characters and impossible-to-spawn items.
Zoen @ www.rpgforums.com
By Siouxdax regarding JSP:
Q u o t e: . . . a forum run by an idiot for idiots . . .