How to update a chart when the array is updated

Question

Hi I am using an array to populate a chart in FB3 and having trouble updating the chart when the array is updated.
Chart
         <mx:Label id="archiveTitle" x="10" y="10" text="Current Archive " fontSize="14" fontWeight="bold"/>
         <mx:PieChart id="chart" height="130" width="300" color="0x323232"
            showDataTips="false" dataProvider="{ratingAC}"  y="22">
             <mx:series>
                <mx:PieSeries field="Rating"/>
            </mx:series>
        </mx:PieChart>
Array + Vars
         [Bindable]
         public var newsDB:ArrayCollection = mx.core.Application.application.newsDB as ArrayCollection;
         [Bindable]
         private var positive:int = 1;
         [Bindable]
         private var neutral:int = 0;
         [Bindable]
         private var negative:int = 0;
         [Bindable]
         private var ratingAC:ArrayCollection = new ArrayCollection([
         { Rating: 1 },  // no data
         { Rating: positive }, // [0] positive
         { Rating: neutral }, // [1] neutral
         { Rating: negative }  // [2] negative
        private function init():void{
               buildChart();
               newsDB.addEventListener(CollectionEvent.COLLECTION_CHANGE, test);
               newsDB.addEventListener(CollectionEvent.COLLECTION_CHANGE, buildChart);
        private function test(e:CollectionEvent):void{
             trace("array changed");
             positive = 20
        private function buildChart(e:CollectionEvent=null):void{
             for(var i:int; i<newsDB.length; i++){
                  if(newsDB[i].rateItem == 0){
                       trace(positive);
                       positive += 1;
                       //ratingAC.setItemAt(positive,0);
                       trace(positive);
                  if(newsDB[i].rateItem == 1){
                       neutral += 1;
                  if(newsDB[i].rateItem == 2){
                       negative += 1;

Answer 1

Sorry, in my app I have an ArrayCollection of items from a news feed that the user has deemed important, and given each item a rating. The For loop will loop through the "newsDB" array and set the var accordingly (positive, negative, neutral). The variables are what is populating the arrayCollection (ratingAC). How would I either a) bind the variables to the ArrayCollection so that it updates when one has changed, or b) update the specific index in the array collection. When debugging, i notice that the variables are updating, but the arrayCollection is not.
Thanks in advance!