EN_KILLFOCUS

This code specifies that the edit control has lost the input focus. The control's parent window receives this code through a WM_COMMAND message from the control.

Parameter Description  

wParam Contains the wParam parameter of the WM_COMMAND message, and specifies the control ID.  
lParam Contains an edit-control window handle in its low-order word and the EN_KILLFOCUS code in its high-order word.