On next code:

Expected : scroll the listbox

Observed : do none

* Mousewheel
 LPARAMETERS nDirection, nShift, nXCoord, nYCoord
NODEFAULT 
RETURN ListBox::MouseWheel(nDirection, nShift, nXCoord, nYCoord)

Why of this code:
Example: Scroll a ListBox without focus.

I known the TopIndex workaround.

Fabio