$PLOT->CanvasBind("<ButtonPress-3>", 
                   [sub {
                        my ($canv,$x,$y)=@_;  
                        $x=$canv->canvasx($x);
                        $y=$canv->canvasy($y);                         
                        $MOVING_IN_PROGRESS=1;
                        $canv->createLine($x,$y,$x,$y,-tag=>'zoombox');
                        ($xlock2,$ylock2)=($x,$y)
                   }, Ev('x'), Ev('y')]);  

  $PLOT->CanvasBind("<ButtonRelease-3>", 
                   [sub {
                        my ($canv,$x,$y)=@_;                         
                        if ($MOVING_IN_PROGRESS==1) {
                          $x=$canv->canvasx($x);
                          $y=$canv->canvasy($y);
                          ($x,$y)=(($x-$xzero)/$xscale,-($y-$yzero)/$yscale);
                          ($xlock2,$ylock2)=(($xlock2-$xzero)/$xscale,-($ylock2-$yzero)/$yscale);
                          $XMIN=$XMIN+($x-$xlock2);
                          $XMAX=$XMAX+($x-$xlock2);
                          $YMIN=$YMIN+($y-$ylock2);
                          $YMAX=$YMAX+($y-$ylock2);
                          plot($plot_f_ref,$plot_ref,$data_ref);                       
                          $MOVING_IN_PROGRESS=0;
                        }                                             
                   }, Ev('x'), Ev('y')]);