The EN_KILLFOCUS notification message is sent when an edit control loses the keyboard focus. The parent window of the edit control receives this notification message through the WM_COMMAND message.
EN_KILLFOCUS
idEditCtrl = (int) LOWORD(wParam); // identifier of edit control
wNotifyCode = HIWORD(wParam); // notification code
hwndEditCtrl = (HWND) lParam; // handle of edit control
Windows NT: Requires version 3.1 or later.
Windows: Requires Windows 95 or later.
Windows CE: Requires version 1.0 or later.
Header: Declared in winuser.h.
Edit Controls Overview, Edit Control Messages, EN_SETFOCUS, WM_COMMAND