Using The Summary Function in ADG

Question

Hello All,
Please see my code below. Im using the advance data grid to create a summary row. The summary row currenty SUMs up the 'unqiuevists' and 'redemptions' columns and all is working well.
What i want to do is then create a 3rd row called 'conversion rate' this conversion rate is a calculation between the uniquevisits and the redemptions columns. If you review the code at the bottom I have managed to create a custom summary func and that function seems to be working fine (using trace)..
However, I cannot then get the calculated result back into the advance data grid, am i missing something really obvious or is what Im trying to do not possible using the summary row function?
Please try and help, Ive been on this for days!
Thanks
<?xml version="1.0"?>
<!-- dpcontrols/adg/SummaryGroupADGCustomSummary.mxml -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" initialize="createGrouping(dpFlat)">
    <mx:Script>
        <![CDATA[
            import mx.collections.GroupingField;
            import mx.collections.Grouping;
            import mx.collections.SummaryField;
            import mx.collections.SummaryRow;
            import mx.collections.GroupingCollection;
            import mx.collections.ArrayCollection;
            import mx.controls.advancedDataGridClasses.AdvancedDataGridColumn;
            import mx.collections.IViewCursor;    
            import mx.collections.SummaryObject;
            private var groupingCollection:GroupingCollection = new GroupingCollection();
            private function createGrouping(tmpArray:ArrayCollection):GroupingCollection
                groupingCollection.source = tmpArray;
                var summaryRow:SummaryRow = new SummaryRow;
                var summaryField:SummaryField = new SummaryField;
                summaryField.dataField="redemptions";
                summaryField.operation="SUM";
                var summaryField1:SummaryField = new SummaryField;
                summaryField1.dataField="newvisits";
                summaryField1.operation="SUM";
                var summaryField2:SummaryField = new SummaryField;
                summaryField2.dataField="conversionrate";
                summaryField2.summaryFunction = summFunc;
                summaryRow.fields = [summaryField,summaryField1,summaryField2];
                summaryRow.summaryPlacement = "group";
                summaryRow.summaryObjectFunction = summObjFunc;
                var grouping:Grouping = new Grouping();
                var groupingField:GroupingField = new GroupingField("site");
                var groupingField1:GroupingField = new GroupingField("merchant");
                grouping.fields=[groupingField,groupingField1];
                groupingField.summaries = [summaryRow];
                groupingField1.summaries = [summaryRow];
                groupingCollection.grouping = grouping;
                groupingCollection.refresh();
                return groupingCollection;
           [Bindable]
            private var dpFlat:ArrayCollection = new ArrayCollection([
              {site:"BBVA", merchant:"TALLINK", Offer:"10% Off", newvisits:38865, redemptions:40000},
              {site:"BBVA", merchant:"LIVEIT", Offer:"10% Off", newvisits:29885, redemptions:30000}, 
              {site:"CartaSi", merchant:"Central California", Offer:"10% Off", newvisits:29134, redemptions:30000}, 
              {site:"CartaSi", merchant:"Nevada", Offer:"10% Off", newvisits:52888, redemptions:45000}, 
              {site:"BarclayCard", merchant:"Northern California", Offer:"10% Off", newvisits:38805, redemptions:40000},
              {site:"BarclayCard", merchant:"Northern California", Offer:"10% Off", newvisits:55498, redemptions:40000}, 
              {site:"Nordea", merchant:"Southern California", Offer:"10% Off", newvisits:44985, redemptions:45000},
              {site:"Nordea", merchant:"Southern California", Offer:"10% Off", newvisits:44913, redemptions:45000},
              {site:"BBVA", merchant:"TALLINK", Offer:"10% Off", newvisits:38865, redemptions:40000},
              {site:"BBVA", merchant:"LIVEIT", Offer:"10% Off", newvisits:29885, redemptions:30000}, 
              {site:"CartaSi", merchant:"Central California", Offer:"10% Off", newvisits:29134, redemptions:30000}, 
              {site:"CartaSi", merchant:"Nevada", Offer:"10% Off", newvisits:52888, redemptions:45000}, 
              {site:"BarclayCard", merchant:"Northern California", Offer:"10% Off", newvisits:38805, redemptions:40000},
              {site:"BarclayCard", merchant:"Northern California", Offer:"10% Off", newvisits:55498, redemptions:40000}, 
              {site:"Nordea", merchant:"Southern California", Offer:"10% Off", newvisits:44985, redemptions:45000},
              {site:"Nordea", merchant:"Southern California", Offer:"10% Off", newvisits:44913, redemptions:45000},
            private function summFunc(cursor:IViewCursor, dataField:String,
                operation:String):Number {
                var conversionrate:Number = 0;
                conversionrate +=  (cursor.current["redemptions"] / cursor.current["newvisits"]) * 100
                trace (dataField)
                trace (conversionrate);      
                return conversionrate;
             private function summObjFunc():SummaryObject {
                // Define the object containing the summary data.
                var obj:SummaryObject = new SummaryObject();
                // Add a field containing a value for the Territory_Rep column.
                obj.conversionrate2 = "Alternating Reps";
                return obj;
      ]]>
    </mx:Script>
    <mx:DataGrid id="test" dataProvider="{dpFlat}">
    </mx:DataGrid>
    <mx:AdvancedDataGrid id="myADG"  width="100%" height="100%"  dataProvider="{createGrouping(dpFlat)}">       
        <mx:columns>
            <mx:AdvancedDataGridColumn dataField="site"/>
            <mx:AdvancedDataGridColumn dataField="offer"/>
            <mx:AdvancedDataGridColumn dataField="newvisits"/>
            <mx:AdvancedDataGridColumn dataField="redemptions"/>
            <mx:AdvancedDataGridColumn dataField="conversionrate"/>
            <mx:AdvancedDataGridColumn dataField="conversionrate2"/>
        </mx:columns>
   </mx:AdvancedDataGrid>
    <mx:Button label="Button" click="groupingCollection.refresh()"/>
</mx:Application>

Answer 1

For those who are interested this is the corrected custom summary function -
private function summFunc(cursor:IViewCursor, dataField:String,
                operation:String):Number {
                var totalNewVisits:Number = 0
                var totalNewRedemptions:Number = 0
                var tmpVisits:Number = 0;
                var tmpRedemptions:Number = 0;      
                while (!cursor.afterLast)
                    tmpVisits = cursor.current["newvisits"];
                    totalNewVisits += tmpVisits;
                    tmpRedemptions = cursor.current["redemptions"];
                    totalNewRedemptions += tmpRedemptions;
                    cursor.moveNext()
                var conversionrate:Number = 0;
                conversionrate =  (totalNewRedemptions / totalNewVisits) * 100
                return conversionrate;