assign a certain media tray on command line

[ekkard gerlach]

CUPS offers ordinaryly upper, lower, MultiPurpose, LargeCapacity  as 
media tray selection, e.g. lp -o media=A4,lower filename. The laser 
printer brother HL 5270 offers 3 cassettes (maximum). How can I assign 
cassette Nr. 3 on command line?

ppd-file from brother:
[...]
*UIConstraints: *OptionTrays 1Trays *InputSlot Tray2^M
*UIConstraints: *InputSlot Tray2 *OptionTrays 1Trays^M
*UIConstraints: *OptionTrays 1Trays *InputSlot Tray3^M
*UIConstraints: *InputSlot Tray3 *OptionTrays 1Trays^M
*UIConstraints: *OptionTrays 2Trays *InputSlot Tray3^M
*UIConstraints: *InputSlot Tray3 *OptionTrays 2Trays^M
[...]

Applications like Openoffice read the ppd-file and offer all available 
options, e.g. cassette Nr.3.
How does OpenOffice print the document to cassette Nr. 3? The parameters 
OpenOffice uses is that what I want to know.

thx
Ekkard