Refresh a BarChart after adding a BarSeries
<mx:BarChart id="barchart" dataProvider="{model.myList}" type="clustered">
    <mx:horizontalAxis>
        <mx:LinearAxis autoAdjust="true"/>
    </mx:horizontalAxis>
    <mx:verticalAxis>
        <mx:CategoryAxis categoryField="name"/>
    </mx:verticalAxis>
    <mx:series>
        <mx:BarSeries dataProvider="{model.myList}" xField="myValue"/>
    </mx:series>
</mx:BarChart>

var barSerie:BarSeries = new BarSeries();
barSerie.dataProvider = model.myList;
barSerie.xField = "myCalculatedValue";
barchart.series.push(barSerie);

var barSerie:BarSeries = new BarSeries();
barSerie.dataProvider = model.myList;
barSerie.xField = "myCalculatedValue";
var allSeries:Array = barchart.series;
allSeries.push(barSerie);
barchart.series = allSeries;

public function set series(value:Array /* of Series */):void
{
    value = value == null ? [] : value;
    _userSeries = value;

    var n:int = value.length;
    for (var i:int = 0; i < n; ++i)
    {
        if (value[i] is Series)
        {
            (value[i] as Series).owner = this;
        }
    }

    invalidateSeries();
    invalidateData();
    legendDataChanged();
}