使控件失去焦点

三种方式任一种：

GetDlgItem(要失去焦点的控件名)->PostMessage(WM_KILLFOCUS, 0, 0);
::SendMessage(GetDlgItem(要失去焦点的控件名)-> m_hWnd,WM_KILLFOCUS,-1,0);
 SendDlgItemMessage(要失去焦点的控件名,WM_KILLFOCUS,0,0);