BWidget NoteBook: Retrieve current page?

I'm relatively new to Tk (and I don't actually program in tcl -- I use
the ruby bindings. But I puzzle my way along; tcl's not too hard to read
(I couldn't write it if I tried, though!))

Anyway, I need some way to find which tab's the current tab in a BWidget
NoteBook.

I've tried fiddling with bindtabs (the ruby binding calls it tabbind,
and has some other stuff like tabbind_append and tabbind_remove; I'm not
exactly sure what they do) to no fruition. Would someone help me out here?

Thanks,

--
- nornagon