How to access checkbox in mx:list

Question

I'm trying to access the checkboxes in my list
<mx:List itemRenderer="mx.controls.CheckBox" x="0" y="153" id="listVocab" height="297" width="313"></mx:List>
but I can't find a way. This is what I'm doing
        for(var i:int = 0 ; i < listVocab.numChildren; i++)
                if (  I want to access the checkbox here to see if it's checked  then do the below but I don't know how to access the checkboxes??? )
                // This gives me access to the text but                 
               var word:String = listVocab.dataProvider[i].toString() ;

Answer 1

Problem is with dataProvider your assigning to dataGrid is of type Array of Strings so thats why its saying selected property is not available on String.
Code given above by me will work for arrayCollection having objects of following type instead of just plain strings:
public class CustomClass
         public var data:String; // here id you can store
        public var label:String; // here word you can store
        public var selected:Boolean;
You can make modification to
public class CustomVocabulary
        public var sentence:String;
        public var type:String;
        public var dbId:String;
        public var words:ArrayCollection; // this will contain objects of type CustomClass.
<mx:List id="list" dataProvider="{ customVocabulary.words }"