Flex LINE Chartのdata TipFunction

<?xml version="1.0"?>
<!-- charts/HitDataCastingWithPercent.mxml -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" initialize=
"init()">
  <mx:Script><![CDATA[
     import mx.collections.ArrayCollection;
     import mx.charts.HitData;
     import mx.charts.series.ColumnSeries;
     import mx.charts.series.items.ColumnSeriesItem;

     [Bindable]
     public var dataSet:ArrayCollection = new ArrayCollection([
        {Month:"Jan", Income:1500, Profit:90},
        {Month:"Feb", Income:1200, Profit:100},
        {Month:"Mar", Income:750, Profit:150}
     ]);

     public var b:Boolean = true;

     public function myDataTipFunction(e:HitData):String {

        var s:String;
        s = "<B>" + [b]ColumnSeries(e.element).displayName[/b] + "</B>
";

        s += "<I>Income:</I> <FONT COLOR='#339966'>$" + 
            e.item.Income + "</FONT>
";
        s += "<I>Expenses:</I> <FONT COLOR='#FF0000'>$" + 
            (e.item.Income - e.item.Profit) + "</FONT>
";
        s += "------------------------
";
        s += "<I>Profit:</I> $" + e.item.Profit + "
";

        // The value of the Income will always be 100%, 
        // so exclude adding that to the DataTip. Only 
        // add percent when the user gets the Profit DataTip.
        var percentValue:Number =
            Number(ColumnSeriesItem(e.chartItem).yValue);
        if (percentValue < 100) {
            s += "Profit was equal to about <B>" + 
                Math.round(percentValue) + "</B>% of the income.
";
        }
        return s;

        //return e.item.Month + ":<B>$" + e.item.Profit + "</B>";
     }
  ]]></mx:Script>
  <mx:Panel title="Accessing ChartItems from HitData Objects">
     <mx:ColumnChart id="myChart" 
        dataProvider="{dataSet}" 
        type="100%"
        dataTipFunction="myDataTipFunction" 
        showDataTips="true"
     >
        <mx:horizontalAxis>
           <mx:CategoryAxis categoryField="Month"/>
        </mx:horizontalAxis>
        <mx:series>
           <mx:ColumnSeries 
                yField="Profit" 
                displayName="Profit '06"
           />
           <mx:ColumnSeries 
                yField="Income" 
                displayName="Income '06"
           />
        </mx:series>
     </mx:ColumnChart>
     <mx:Legend dataProvider="{myChart}"/>
  </mx:Panel>
</mx:Application>