Locking an option in a PPD file?

[ralf.hildebrandt at charite.de]

We have an NRG DSm635 PXL printer that has a "JobType=DocServer".

In that mode the files are not printed directly, but instead the users' data is being spooled to a hard disk on the printer and ONLY printed, after the user paid for printing them.

That's neat.

But I want to lock down that option in the *.ppd file so the users cannot choose to print directly.

How can I do that?