I dont even think Longhorn Server can be configured that way jsut yet. As i said it is in Beta stages and not everything is fully operational.
Best bet is to contact M$ and ask them. Since you have a copy of it you should be in the Beta program and be able to ask them.
Otherwise i think you will be outta luck since i have not been able to do much with Longhorn Server except set up a File, Email, and Data Server with it.