WindowRef

will:

local hwnd:int = QueryGadget( window, QUERY_HWND )

return a WindowRef? I have a small piece of "C" that requires a WindowRef to be passed to it but using the above code nothing happens?

Not QUERY_HWND on the Mac...

From gadget.bmx

Const QUERY_HWND=1
Const QUERY_HWND_CLIENT=2
Const QUERY_NSVIEW=3
Const QUERY_NSVIEW_CLIENT=4
Const QUERY_FLWIDGET=5
Const QUERY_FLWIDGET_CLIENT=6

No, I don't know why there are different ones - especially as only one is ever valid at a time.
... I'd go for number 3 ;-)