Accessing children of element created with PopUpManager

Question

My application has 2 files. First one is main application, second one is custom component (Popup) used to create popup windows. I would like to know how can i access ViewStack element (has id assigned to "vs") in popup from main application.
NB! Lot of code has been removed for readability!
application.mxml
<s:Application creationComplete="init()">
     <fx:Script>
          <![CDATA[
                    public function init():void{
                         var popup:TitleWindow = PopUpManager.createPopUp(this , Popup , false) as TitleWindow;
                         trace(popup.vs , "It's not working!!");
          ]]>
     </fx:Script>
</s:Application>
Popup.mxml
<s:TitleWindow>
     <mx:ViewStack id="vs">
     </mx:ViewStack>
</s:TitleWindow>

Answer 1

<s:Application creationComplete="init()">
     <fx:Script>
          <![CDATA[
                    public function init():void{
                         var popup:Popup= PopUpManager.createPopUp(this , Popup , false) as Popup;
                         popup.vs // should get access
          ]]>
     </fx:Script>
</s:Application>
Can you please try the above.