An application sends the LBN_SELCANCEL notification message when the user cancels the selection in a list box. The parent window of the list box receives this notification message through the WM_COMMAND message.
LBN_SELCANCEL idListBox = (int) LOWORD(wParam); // identifier of list box hwndListBox = (HWND) lParam; // handle of list box
This notification message applies only to list boxes of the LBS_NOTIFY style.