flex中datagrid合龙单元格

flex中datagrid合并单元格
形如： A  B  C
       1  2  3
       1  2  3
       1  2  3
       1  2  3
采用flex中的datagrid，现有字段A,B,C，我想合并A,B这两个标题头。也就是说标题头有两列，而下边的数据还是三列，怎么实现啊，小弟初学flex，高手指教啊！
------解决方案--------------------
<mx:AdvancedDataGrid id="adg1" designViewDataType="flat" sortExpertMode="true" sortableColumns="false" dataProvider="{arrGrid}" width="100%" height="100%">
<mx:groupedColumns>

<mx:AdvancedDataGridColumnGroup headerText="上午">
<mx:AdvancedDataGridColumn headerText="上班"/>
<mx:AdvancedDataGridColumn headerText="下班" />
</mx:AdvancedDataGridColumnGroup>
<mx:AdvancedDataGridColumnGroup headerText="下午">
<mx:AdvancedDataGridColumn headerText="上班"/>
<mx:AdvancedDataGridColumn headerText="下班"/>
</mx:AdvancedDataGridColumnGroup>
</mx:groupedColumns>
</mx:AdvancedDataGrid>
------解决方案--------------------

//生成Advancedatagrid

		public function getForecastAdvancedDataGrid(tmpMonthADGDataGrid:AdvancedDataGrid,

						forecastData:ForecastData):void{

			var i:int;				

			

			myadgmonthdata=new ArrayCollection();

			

			var tmpD:AdvancedDataGridColumn=new AdvancedDataGridColumn();

			tmpD.headerText="D";

			tmpD.width=90;

			tmpD.itemRenderer=new ClassFactory(deleteButton);

			

			var tmpProduct:AdvancedDataGridColumn=new AdvancedDataGridColumn("Product");

			tmpProduct.dataField="1";

			tmpProduct.width=100;

			tmpProduct.dataField="product";



			myadgmonthdata.addItem(tmpD);

			myadgmonthdata.addItem(tmpProduct);

			

			for(i=1;i<(int(forecastData.forecast_month_count)+1);++i){

				var tmpGroup:AdvancedDataGridColumnGroup=new AdvancedDataGridColumnGroup();

				

				tmpGroup.headerText=myMonth.getMonth(i,forecastData.forecast_forecast);

				

				var tmpqty:AdvancedDataGridColumn=new AdvancedDataGridColumn();

				tmpqty.headerText="QTY";

				tmpqty.width=60;

				tmpqty.dataField="qty"+i.toString();

				var tmpup:AdvancedDataGridColumn=new AdvancedDataGridColumn();

				tmpup.headerText="U/P";

				tmpup.width=50;

				tmpup.dataField="unitprice"+i.toString();

				var tmpRevenue:AdvancedDataGridColumn=new AdvancedDataGridColumn();

				tmpRevenue.headerText="Revenue";

				tmpRevenue.width=80;

				tmpRevenue.dataField="revenue"+i.toString();

				var tmptestqty:AdvancedDataGridColumn=new AdvancedDataGridColumn();

				tmptestqty.headerText="TesterQTY";

				tmptestqty.width=90;

				tmptestqty.dataField="testerqty"+i.toString();



				tmpGroup.children=tmpGroup.children.concat(tmpqty);

				tmpGroup.children=tmpGroup.children.concat(tmpRevenue);

				tmpGroup.children=tmpGroup.children.concat(tmptestqty);

				tmpGroup.children=tmpGroup.children.concat(tmpup);

				

				myadgmonthdata.addItem(tmpGroup);

			}

			

			var tmpTester:AdvancedDataGridColumn=new AdvancedDataGridColumn();

			tmpTester.headerText="Tester";

			tmpTester.width=70;

			tmpTester.dataField="tester";

			

			var tmpHRA:AdvancedDataGridColumn=new AdvancedDataGridColumn("HR(A)");

			tmpHRA.dataField="hr_a";

			tmpHRA.width=60;

			

			var tmpUPD:AdvancedDataGridColumn=new AdvancedDataGridColumn("UPD");