Change example for C++ 4.0 and later

Typically, you would use this event to flag changed image data and prompt the user to save the changes before closing a window or exiting an application. That use of the event cannot be tested properly without writing a complete application; so this example just shows you a simple test of the event.

void CTutorDlg::OnChangeLead1() 
{
    // TODO: Add your control notification handler code here
    MessageBox("Image data has changed", "Test Message", MB_OK);
}