Tree Control - Access issue

<mx:Script>
		<![CDATA[
public function callPopUp(e:MouseEvent):void
			{
            	 var pop:TitleWindow = TitleWindow(PopUpManager.createPopUp(this,userentry,true)); 
            }
               
		]]>
	</mx:Script> 

<mx:AdvancedDataGrid id="frameworkGrid" dataProvider="{argumentData}" variableRowHeight="true" top="{descriptionText.height+21}" right="20" bottom="10" left="20">
		<mx:columns>
<mx:AdvancedDataGridColumn dataField="@image" headerText="" width="25" >
				<mx:itemRenderer>
                   <mx:Component>
                   		<mx:Image source="@image" mouseMove="{callPopup(event)}"/>
                   </mx:Component>
                </mx:itemRenderer>	
			</mx:AdvancedDataGridColumn>
</mx:columns>
	</mx:AdvancedDataGrid>

                                              

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<?xml version="1.0" encoding="utf-8"?>
<mx:VBox 
    xmlns:mx="http://www.adobe.com/2006/mxml" 
    horizontalAlign="center" verticalAlign="middle"
    width="100%" height="140"
>
    <mx:Image source="@image" mouseMove="callPopup(event)" />
    
	<mx:Script>
		<![CDATA[
			import mx.containers.TitleWindow;
			import mx.managers.PopUpManager;
			
            public function callPopup(e:MouseEvent):void{
               var pop:TitleWindow = TitleWindow(PopUpManager.createPopUp(this, userentry ,true)); 
            }
		
		]]>
	</mx:Script>
    
</mx:VBox>

                                              

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<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
layout="absolute" xmlns:com="*" creationComplete="onCreationComplete()" width="1000" height="650">
<mx:HTTPService id="frameworkService" url="data/arguments.xml" result="frameworkServiceResult(event)" fault="serviceFault(event)" />
	
	<mx:Script>
		<![CDATA[
			import mx.collections.HierarchicalData;
			import mx.collections.XMLListCollection;
			import mx.rpc.events.FaultEvent;
			import mx.rpc.events.ResultEvent;
			import mx.core.IFlexDisplayObject;
            import mx.containers.TitleWindow;
            import mx.managers.PopUpManager;
            import mx.collections.ArrayCollection;
            import mx.controls.Alert;
			
			[Bindable]
			public var description:String;
			[Bindable]
			public var argumentCollection:XMLListCollection;
			[Bindable]
			public var argumentList:XMLList;
			[Bindable]
			public var argumentData:HierarchicalData;
			
			          
			private function onCreationComplete():void
			{
				frameworkService.send();
			}
			
			private function frameworkServiceResult(event:ResultEvent):void
			{
				var xml:XML = new XML(event.message.body);
				argumentList = xml.category;
				argumentCollection = new XMLListCollection(argumentList);
				argumentData = new HierarchicalData(argumentList);
			}
			
			private function serviceFault(event:FaultEvent):void
			{
				trace(event.fault.faultString);
			}
			
			public function callPopUp(e:MouseEvent):void
			{
            	 var pop:TitleWindow = TitleWindow(PopUpManager.createPopUp(this,PopUp,true)); 
            }
               
		]]>
	</mx:Script>
	
	<mx:Style>
    AdvancedDataGrid {
        folderClosedIcon: ClassReference(null);
        folderOpenIcon: ClassReference(null);
    }
	</mx:Style>
	
	<mx:Text id="descriptionText" text="{description}" x="14" width="500" />
	<mx:AdvancedDataGrid id="frameworkGrid" dataProvider="{argumentData}" variableRowHeight="true" top="{descriptionText.height+21}" right="20" bottom="10" left="20">
		<mx:columns>
			<mx:AdvancedDataGridColumn dataField="@category" headerText="Category" width="400" />
			 <mx:AdvancedDataGridColumn dataField="@image" headerText="" width="25" itemRenderer="CallImage" />
			<mx:AdvancedDataGridColumn dataField="@warning" headerText="" width="20">
				<mx:itemRenderer>
                   <mx:Component>
                            <mx:Image source="@warning" maintainAspectRatio="true" width="10" height="10"/>
                   </mx:Component>
                </mx:itemRenderer>	
			</mx:AdvancedDataGridColumn>
			<mx:AdvancedDataGridColumn wordWrap="true" headerText="" width="80">
			<mx:itemRenderer>
                  <mx:Component>
                   <mx:ComboBox>
                  	<mx:dataProvider>
                        <mx:String>Pending</mx:String>
                        <mx:String>Fail P1</mx:String>
                        <mx:String>Fail P2</mx:String>
                        <mx:String>Fail P3</mx:String>
                        <mx:String>Pass</mx:String>
                        <mx:String>NA</mx:String>
                        <mx:String>Waived</mx:String>
                	</mx:dataProvider>
                    </mx:ComboBox>
                   </mx:Component>
                </mx:itemRenderer>					
			</mx:AdvancedDataGridColumn>
			<mx:AdvancedDataGridColumn dataField="@last_response" itemRenderer="mx.controls.Text" wordWrap="true" headerText="Last Response" />
			
		</mx:columns>
	</mx:AdvancedDataGrid>
</mx:Application>

                                              

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//callImage.mxml 
<?xml version="1.0" encoding="utf-8"?>
<mx:VBox 
    xmlns:mx="http://www.adobe.com/2006/mxml" 
    horizontalAlign="center" verticalAlign="middle"
    width="100%" left="200">
  
         <mx:Script>
            <![CDATA[
            import flash.events.MouseEvent; 
            import mx.containers.TitleWindow;
            import mx.managers.PopUpManager;
            import mx.controls.Alert;
            import mx.collections.HierarchicalData;
			import mx.collections.XMLListCollection;
            
            private var point1:Point = new Point();            
            
            [Bindable]
			public var dataField:String = dataField;
			[Bindable]
			public var argumentList:XMLList;
			[Bindable]
			public var argumentData:HierarchicalData;
			
			
            public function callPopup(e:MouseEvent):void{
                var pop:TitleWindow = TitleWindow(PopUpManager.createPopUp(this, PopUp ,true));
                point1.x=img.x;
                point1.y=img.y;                
                point1=img.localToGlobal(point1);
                pop.x=point1.x+15;
                pop.y=point1.y+15;
                //Alert.show(""+data);          
            }
            
                          
                ]]>
        </mx:Script>
  <mx:Image id="img" source="images/imageIcon.png" mouseMove="callPopup(event)"/>
    
</mx:VBox>

                                              

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