flex datagrid....Action Script

Question

public var dataGrid:DataGrid = new DataGrid();           
   dataGrid.dataProvider = gridDataFeed.set;
        dataGrid.id ="dataGrid";
        dataGrid.percentWidth = 150;
        dataGrid.minColumnWidth=120;
        dataGrid. editable=true;
        dataGrid.percentHeight = 75;
        dataGrid.addEventListener( mx.events.DataGridEvent.ITEM_FOCUS_IN, getCellData); 
        var cols:Array = new Array();
        for(var i:int=0;i<gridDataFeed.series.name.length();i++)
        {
         var dgColumn:DataGridColumn = new DataGridColumn();
         dgColumn.dataField =gridDataFeed.series.name[i];
         dgColumn.headerText  = gridDataFeed.series.name[i].@seriesName;
         if(dgColumn.headerText=="Rank")
         {
            dgColumn.editable=true;
         }
         else
         {
            dgColumn.editable=false;
         }
                cols.push(dgColumn);
        }
        dataGrid.columns = cols;
        bx1.addChild(dataGrid);

getCellData in that function i need alert.....or else can i use any other event handler

this the code ...in that Rank column is editable ...when i click on any item in that column i need alert the clicked item before editing ...and after editing also i have alert the new value........how to to this