As a first Test:
Uncheck red circled Checkbox in Properties of Printer and run your code.
If it's disabled, you at least found the Property of the Printer itself
No idea though, how to pass that from code.
I'd look for a Property of the Printer-Class/Dialog-Box which might be it
Everything said: It's not a Property of the Dialog-Box, but of the Printer itself.
Since the DialogBox enumerates all available Printers, i'd go searching there