LBN_SETFOCUS
idListBox = LOWORD(wParam);
hwndListBox = (HWND)lParam;
The LBN_SETFOCUS notification message is sent when a list box receives the input focus. The parent window of the list box receives this notification message through a WM_COMMAND message.
idListBox
Value of low word of wParam. Specifies the list-box ID.
hwndListBox
Value of lParam. Specifies the list-box window handle.
WM_COMMAND