Newbie: How to access class instance from childSWF

Hi
I got a child swf that needs to access a public static function in my “main” class, in parent swf.
When i compile the child SWF with code myApp.myFunction() it says it does not know what myApp is (logically)
I guess i need to check if parent exist, then “find” the class instance in the parent swf? I’m not sure exactly how…

Edit: I know i could include the class in the child SWF, but that is not what i’m looking for.