CUPS : How to create "virtual printers" ?

Hi,

I have only one printer, but I want to provide several virtual printers : one
in draft mode, one for text and graphic, and one for high quality.

I remember that it was possible to do this in /etc/printcap. But, is it
possible using the web interface of CUPS ? When I try to install a new driver
that share the same usb device (of course, because it is the same printer !), I
can no more chose the usb device.

I don't know where to search. Could you help me ?

Thanks.

Guillaume