Printer accounting and cutoff for UNIX. Is it possible?

[Ed de Wild]

At our department (information systems) a large number of students are
working on Unix systems (Sun, HP). These systems are connected via
ethernet. On the system we have a number of laser printers. At the moment,
students are wasting enormous amounts of paper using the laser printers.
We would like to limit their use of the printers.

Unix does accounting for the printers. Question: is it possible to check
for the number of printed pages and perform a "budget cutoff" when the
allowed number of pages is surpassed? Does anyone have software for this? 

BTW: Why does UNIX have a cutoff for disk usage (quota) but not for
printer usage?

Any help would be appreciated!