private void axMapControl1_OnMouseMove(object sender,
                                               IMapControlEvents2_OnMouseMoveEvent e)
        {
            if (e.button != 1)
            {
                return;
            }
            IPoint pPoint = new ESRI.ArcGIS.Geometry.Point();

            pPoint.PutCoords(e.mapX, e.mapY);
            m_mapControl.CenterAt(pPoint);
            m_mapControl.ActiveView.PartialRefresh(
                esriViewDrawPhase.esriViewGeography, null, null);
        }