      *  @see mx.components.baseClasses.FxTrackBase#setValue()
      *  @see mx.core.IViewport
      *  @see mx.core.IViewport#horizontalScrollPosition
-     *  @see mx.core.IViewport#horizontalScrollPositionDelta()
+     *  @see mx.core.IViewport#getHorizontalScrollPositionDelta()
      */
     override public function step(increase:Boolean = true):void
     {
         if (!viewport)
             super.step(increase);
         else
-            updateViewportHSP((increase) ? Keyboard.RIGHT : Keyboard.LEFT);
+            updateViewportHSP((increase) ? ScrollUnit.RIGHT : ScrollUnit.LEFT);
     }   
     
     /**

     *  change the horizontal scroll position for line up or line down by 
     *  scrolling the viewport.
     *  This method calculates the amount to scroll by calling the 
     *  <code>IViewport.horizontalScrollPositionDelta()</code> method 
     *  with either <code>flash.ui.Keyboard.RIGHT</code> 
     *  or <code>flash.ui.Keyboard.LEFT</code>.
     *  It then calls the <code>setValue()</code> method to 

     *  @see mx.components.baseClasses.FxTrackBase#setValue()
     *  @see mx.core.IViewport
     *  @see mx.core.IViewport#horizontalScrollPosition
     *  @see mx.core.IViewport#getHorizontalScrollPositionDelta()
     */
    override public function page(increase:Boolean = true):void
    {
        if (!viewport)
            super.page(increase);
        else
            updateViewportHSP((increase) ? ScrollUnit.PAGE_RIGHT : ScrollUnit.PAGE_LEFT);
    }
    
    /**
