' Make the form topmost or not.
Private Sub SetOnTop(Optional ByVal on_top As Boolean = _
    True)
    If on_top Then
        SetWindowPos hwnd, _
            HWND_TOPMOST, 0, 0, 0, 0, _
            SWP_NOMOVE + SWP_NOSIZE
    Else
        SetWindowPos hwnd, _
            HWND_NOTOPMOST, 0, 0, 0, 0, _
            SWP_NOMOVE + SWP_NOSIZE
    End If
End Sub