private void axPageLayoutControl1_OnMouseDown(object sender, ESRI.ArcGIS.Controls.IPageLayoutControlEvents_OnMouseDownEvent e)
 {
     if (e.button == 1)
     {
         axPageLayoutControl1.Extent = axPageLayoutControl1.TrackRectangle();
     }
     else if (e.button == 2)
     {
         axPageLayoutControl1.Pan();
     }
 }