Since I just spent the better part of a week banging my head on the wall here is a pointer.

http://maemo.org/api_refs/4.1/gtk+2....set-input-mode

By setting a GtkEntry to be NUMERIC only it will allow easier non-Fn key number entry. entry.set_input_mode( mask )

But your problem might be easier.

http://maemo.org/api_refs/4.1/gtk+2....on-set-numeric

gtkspinbutton.set_numeric( True )

Might also do the trick.

Of course this may or may not work under Python.