[flexcoders] Help trying to sort data provider for DataGrid

[lanekelly5]

I'm trying to load a few elements of an RSS feed into a DataGrid, and I'm 
having trouble with the code to pre-sort the data before the grid gets it.  
Here's a snippet of the code:

private function requestRSS(e:FlexEvent):void
                        {
                                initVars();
                                showBusyCursor();
                                rssService.url = rssUrl;
                                rssService.resultFormat = "e4x";
                                rssService.useProxy = false;
                                rssService.addEventListener(ResultEvent.RESULT, 
resultHandler);
                                rssService.addEventListener(FaultEvent.FAULT, 
faultHandler);
                                rssService.send();
                        }

private function resultHandler(e:ResultEvent):void
                        {
                                listHeadlines.dataProvider = 
e.target.lastResult.channel.item;
                        }

In the mxml:
<mx:DataGrid id="listHeadlines" width="433" height="113" 
click="showDetails(event)">
    <mx:columns>
        <mx:DataGridColumn dataField="pubDate" sortDescending="true"/>
        <mx:DataGridColumn dataField="title"/>
    </mx:columns>
</mx:DataGrid> 

At this point my data in e.target.lastResult.channel.item is not always sorted 
properly.  I'd like to sort it by pubDate descending before filling out the 
DataGrid.  Any guidance on this?