Here’s the class …

package com.gower.amway.components
{
import mx.core.IVisualElement;
import flash.display.DisplayObject;
import flash.display.DisplayObjectContainer;
import flash.display.InteractiveObject;
import flash.events.Event;

import spark.components.HSlider;

public class VolumeHSlider extends HSlider
{
[SkinPart(required="false")]
public var volumeArea:IVisualElement;

private var tempTrackSize:Number = NaN;

public function VolumeHSlider()
{
super();
}

override protected function partAdded(partName:String, instance:Object):void
{
super.partAdded(partName, instance);

if (instance == volumeArea)
{
if (volumeArea is InteractiveObject)
InteractiveObject(volumeArea).mouseEnabled = false;
if (volumeArea is DisplayObjectContainer)
DisplayObjectContainer(volumeArea).mouseChildren = false;

invalidateDisplayList();
}
else if (instance == track)
{
tempTrackSize = NaN;
}
}

override protected function updateDisplayList(unscaledWidth:Number,
unscaledHeight:Number):void
{
super.updateDisplayList(unscaledWidth, unscaledHeight);

sizeVolumeArea(valueToPosition(value) + thumbSize);
}

override protected function track_updateCompleteHandler(event:Event):void
{
super.track_updateCompleteHandler(event);

if (trackSize != tempTrackSize)
{
sizeVolumeArea(valueToPosition(value) + thumbSize);
tempTrackSize = trackSize;
}
}

protected function sizeVolumeArea(volumeAreaSize:Number):void
{
if (volumeArea)
DisplayObject(volumeArea).width = Math.round(volumeAreaSize);
}
}
}