private void TestLocked()
        {
            int  hr;
            bool bLocked, bLocked2;

            hr = m_pVideoGroupObj.GetLocked(out bLocked);
            DESError.ThrowExceptionForHR(hr);

            hr = m_pVideoGroupObj.SetLocked(!bLocked);
            DESError.ThrowExceptionForHR(hr);

            hr = m_pVideoGroupObj.GetLocked(out bLocked2);
            DESError.ThrowExceptionForHR(hr);

            Debug.Assert(bLocked != bLocked2, "Locked");
        }