code: function(evt) {
          if (!OpenLayers.Event.isLeftClick(evt) && !OpenLayers.Event.isSingleTouch(evt)) {
              return;
          }
          this.map.events.on({
              "touchmove": this.passEventToSlider,
              "mousemove": this.passEventToSlider,
              "mouseup": this.passEventToSlider,
              scope: this
          });
          this.mouseDragStart = evt.xy.clone();
          this.zoomStart = evt.xy.clone();
          this.div.style.cursor = "move";
          // reset the div offsets just in case the div moved
          this.zoombarDiv.offsets = null; 
          OpenLayers.Event.stop(evt);
      }
docs: /*
  Method: zoomBarDown
  event listener for clicks on the slider
  
  Parameters:
  evt - {<OpenLayers.Event>}