[python-win32] Push back window (i.e. change its z-order)

[reckoner]

Given a window handle with (x,y,dx,dy) rectangle, I'm trying to push the 
window back (in other words, change its z-order) using the following:

win32gui.SetWindowPos(handle, win32con.HWND_BOTTOM, x, y, dx, dy, 
win32con.SWP_NOMOVE+win32con.SWP_NOSIZE+win32con.SWP_NOREPOSITION)

but it's not working. Nothing happens.

Anybody have any ideas why?

Thanks!