An application sends a CB_GETEDITSEL message to get the starting and ending character positions of the current selection in the edit control of a combo box.
CB_GETEDITSEL wParam = (WPARAM) (LPDWORD) lpdwStart; // receives starting position lParam = (LPARAM) (LPDWORD) lpdwEnd; // receives ending position
The return value is a zero-based 32-bit value with the starting position of the selection in the low-order word and with the ending position of the first character after the last selected character in the high-order word.