An application sends an LB_GETCARETINDEX message to determine the index of the item that has the focus rectangle in a multiple-selection list box. The item may or may not be selected.
wParam
This parameter is not used.
lParam
This parameter is not used.
The return value is the index of the list-box item that has the focus rectangle. If the list box is a single-selection list box, the return value is the index of the selected item, if an item is selected.
LB_SETCARETINDEX