An application sends the LBN_DBLCLK notification message when the user double-clicks a string in a list box. The parent window of the list box receives this notification message through the WM_COMMAND message.
LBN_DBLCLK idListBox = (int) LOWORD(wParam); // identifier of list box hwndListBox = (HWND) lParam; // handle of list box
Only a list box that has the LBS_NOTIFY style will send this notification message.