Can you return a String from a summaryObjectFunction

private function firstValue(itr:IViewCursor,field:String, str:String=null):Object
{
  //if(isNaN(itr.current[field])) return 0  //Theory: Only works on Numeric Values?
  return itr.current[field]
}

(mx:GroupingField name="Offer")
  (mx:summaries)
    (mx:SummaryRow summaryPlacement="group")
      (mx:fields)
        (mx:SummaryField dataField="OfferDescription"   label="OfferDescription" summaryFunction="firstValue"/)
        (mx:SummaryField dataField="OfferID"   label="OfferID" summaryFunction="firstValue"/)
        (/mx:fields)
    (/mx:SummaryRow)
  (/mx:summaries)
(/mx:GroupingField)

private function getNestedItem(item:Object):Object {

    			try {
    				if (item.undefined[0]) {
    					item = getNestedItem(item.undefined[0]);
    				}
    			} catch (e:Error) {
    				// leave item alone
    			}
    			return item;
    		}
    		private function formatColumn(item:Object, column:AdvancedDataGridColumn):String {

    			var output:String;
    			// If this is a summary row
    			if (item.GroupLabel) {

    				item = getNestedItem(item);
    			}

    			switch (column.dataField) {

    				case 'comment':

    					return item.comment;


    			}

    		}