[Newbies] authenticating Squeak to a proxy

Hello,

I am new to Squeak (but not OO programming), and reading the "Squeak by Example" book, but I can't figure out how to get Squeak to use a proxy that requires authentication. When at home, this is not a problem, but at my school, I can only access the Internet through an HTTP proxy, and it requires that each student enter his or her username and password. I've found where in Squeak I need to tell it what port to use, and the server name, but there's nothing there for a username or passkey. Is there a way to tell Squeak to authenticate itself as a particular user?

Thanks, Aidan