Box/Rectangle Draw Selection in Google Maps

I found a Library keydragzoom (http://google-maps-utility-library-v3.googlecode.com/svn/tags/keydragzoom/1.0/docs/reference.html) and used it to draw a rectangle on the page.

Later, I edit the library and stopped it from zooming the selected area and instead made it return the correct co-ordinates in ‘dragend’ event. Then I manually looped through all the marker on the map to find the markers that are within that particular region. The library was not giving me the proper co-ordinates to I made the following changes.

Changed the DragZoom function to

    var prj = null;
    function DragZoom(map, opt_zoomOpts) {
        var ov = new google.maps.OverlayView();

        var me = this;
        ov.onAdd = function () {
            me.init_(map, opt_zoomOpts);
        };
        ov.draw = function () {
        };
        ov.onRemove = function () {
        };
        ov.setMap(map);
        this.prjov_ = ov;
        google.maps.event.addListener(map, 'idle', function () {
            prj = ov.getProjection();
        });
    }

and DragZoom.prototype.onMouseUp_ function to

DragZoom.prototype.onMouseUp_ = function (e) {
    this.mouseDown_ = false;
    if (this.dragging_) {
      var left = Math.min(this.startPt_.x, this.endPt_.x);
      var top = Math.min(this.startPt_.y, this.endPt_.y);
      var width = Math.abs(this.startPt_.x - this.endPt_.x);
      var height = Math.abs(this.startPt_.y - this.endPt_.y);
      var points={
        top: top,
        left: left,
        bottom: top + height,
        right: left + width
       };
      var prj = this.prjov_.getProjection();
      // 2009-05-29: since V3 does not have fromContainerPixel, 
      //needs find offset here
      var containerPos = getElementPosition(this.map_.getDiv());
      var mapPanePos = getElementPosition(this.prjov_.getPanes().mapPane);
      left = left + (containerPos.left - mapPanePos.left);
      top = top + (containerPos.top - mapPanePos.top);
      var sw = prj.fromDivPixelToLatLng(new google.maps.Point(left, top + height));
      var ne = prj.fromDivPixelToLatLng(new google.maps.Point(left + width, top));
      var bnds = new google.maps.LatLngBounds(sw, ne);
      //this.map_.fitBounds(bnds); 
      this.dragging_ = false;
      this.boxDiv_.style.display = 'none';
      /**
       * This event is fired when the drag operation ends. 
       * Note that the event is not fired if the hot key is released before the drag operation ends.
       * @name DragZoom#dragend
       * @param {GLatLngBounds} newBounds
       * @event
       */

      google.maps.event.trigger(this, 'dragend', points);
    }
  };