import mx.collections.*;
public var myArray:Array = ["A", "B", "C", "D", "E", "F"];
[Bindable]
public var myAC:ArrayCollection;
public function initData():void {
myAC = new ArrayCollection(myArray);
}
public function changeCollection():void {
var index4Item:String=String(myAC.getItemAt(4));
myAC.setItemAt("R", 2);
}