Talking to Parent app is not possable

Question

All I want to do is communicate by having my child app talk
to my parent application. I cannot get this to work, and getting
extremely frustrated with this. I cannot find good examples on this
scenerio. Documentation does not seem to provide the details, or I
just don't understand everything within the docs. I have my parent
application talking to my child application, but not the other way
around.
My Main App Has
<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="
http://www.adobe.com/2006/mxml"
layout="absolute">
<mx:Script >
<![CDATA[
import mx.managers.SystemManager;
private var loadedSM:SystemManager;
private function allowInteraction() : void {
loadedSM = SystemManager(swfChild.content);
private function sendData():void {
ChildApp(loadedSM.application).fromMain.text = toChild.text;
]]>
</mx:Script>
<mx:SWFLoader id="swfChild" source="ChildApp.swf"
init="allowInteraction()" y="60" width="261"/>
<mx:Canvas width="278" height="150" id="owner">
<mx:TextInput id="toChild" width="200" height="20"/>
<mx:Button click="sendData();" label="Submit" y="22"
/>
</mx:Canvas>
</mx:Application>
My Child App Has
<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="
http://www.adobe.com/2006/mxml"
layout="absolute">
<mx:Script>
<![CDATA[
public function toParent(): void {
//MainApp(owner).toChild.text = "123";
parentApplication(owner).toChild.text = "123";
//parentApplication.valueOf(toChild.text) = "123"
//local2(owner).fromChild.text = toMain.text;
]]>
</mx:Script>
<mx:Canvas width="204" height="98" x="10" y="10">
<mx:TextArea id="fromMain" width="200" />
<mx:TextInput id="toMain" width="200" y="32" />
<mx:Button label="submit" x="10" y="62"
click="toParent();" />
</mx:Canvas>
</mx:Application>
All I want to do is have each app communicate with each
other? Why is that so hard? What is it that I am missing?
Thanks

Answer 1

Hmm, it is saying that I cannot access the parent item. Is
there something that I need to declare in the parent or child
applications?
TypeError: Error #1009: Cannot access a property or method of
a null object reference.
at ChildApp/toParent()
at ChildApp/___Button1_click()