I can confirm that it is possible for communication between
the container and swf via ExternalInterface when you have the IE
ActiveX flash player control embedded in a Visual C++ app.
This can be taken to the next level by using the
Bridge which allows you to communicate with the SWF by writing
code like oRootObj.Call("getbutton1").Call("addEventListener",
"click", SampleCallback); .
The source code for the bridge can also be used to learn how
to handle ExternalInterface calls in C++.