      *
      *  @private
      */
-    private function updateViewportVSP(unit:uint):void
-    {
-        var delta:Number = viewport.verticalScrollPositionDelta(unit);
+    private function updateViewportVSP(unit:ScrollUnit):void
+    {
+        var delta:Number = viewport.getVerticalScrollPositionDelta(unit);
         setValue(viewport.verticalScrollPosition + delta);
     }
     

     *  change the vertical scroll position for line up or line down by 
     *  scrolling the viewport.
     *  This method calculates the amount to scroll by calling the 
     *  <code>IViewport.verticalScrollPositionDelta()</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 

import flash.ui.Keyboard;
import mx.layout.ILayoutItem;
import mx.layout.LayoutItemFactory;
import mx.components.baseClasses.FxScrollBar;
import mx.core.ScrollUnit;  
import mx.events.PropertyChangeEvent;
import mx.events.ResizeEvent;
import flash.events.Event;
