Determines the index of the item that has the focus rectangle in a multiple-selection list box.
int GetCaretIndex( ) const;
The zero-based index of the item that has the focus rectangle in a list box. If the list box is a single-selection list box, the return value is the index of the item that is selected, if any.
The item may or may not be selected.
See the example for CListBox::SetCaretIndex.