code: function () {
          if (!this.available) { 
              return 0; 
          }
          var newOffset = this.getOffsetFromParent();
          if (YAHOO.lang.isNumber(newOffset[0])) {
              this.lastOffset = newOffset;
              return (newOffset[0] - this.startOffset[0]);
          } else {
              return (this.lastOffset[0] - this.startOffset[0]);
          }
      }
docs: Gets the current X offset from the element's start position in
  pixels.
  @method getXValue
  @return {int} the number of pixels (positive or negative) the
  slider has moved horizontally from the start position.