Paper size format

Hi, I have a problem with an old dos application under
win xp. It run without problems, but I got some problems
in printing. (sorry for my english)
The fact is I can't set a new paper format size in the
printer property, I see I can do it in MS word for
example, but the dos application does't provide this
feature. I tried in every way in the property box of the
printer (Lexmark forms printer 2481) but there's no way.
I can print of course but the paper I use got a different
format compares to the models that windows offer (it's 35
mm width and 35 mm height)
If somebody can help me...I'd appreciate it.

Thanx in advance

Davide Romagnoli