Per-User Printer Access

I administer the computers in a graduate lab. I'm trying to roll out more Kubuntu desktops, but people aren't going to accept them as "regular computers" if they can't print.

The computers in question belong to the lab, and I have root / Local Admin access on them. The printers belong to the school, I have no admin access, and users have to pay for their printing. The protocol is SMB.

On a Windows machine, a user connects to the printer using NT credentials. On Linux, however, I need to supply a username and password in /etc/cups/printers.conf! Thus, any user that prints will be doing so with *my* print credits (and grad students do a lot of printing).

So... I need to be able to add a printer as root (to /etc/cups/printers.conf, for example) in order to pick the right driver, and then let *users* specify their NT username/password when they actually try to use it.