Is it possible to control a Flash movie from JS when you have no control over the source?
I have decompiled the movie to see its inner workings, but I know nothing about Flash, so I'm mostly in the dark.
I found this resource, Interaction with JavaScript, but it's not working for me (probably because I don't know what message to send to the movie).
Controlling a Flash movie with javascript is possible only if the Flash movie has been told to accept commands from javascript. It is done with the addCallBack() method of the ExternalInterface class.
Since you don't have access to the code, your only option is to check the decompiled code for any addCallBack() calls and call those methods from javascript. Unless the original developer intended to allow the movie to be controlled from javascript, he wouldn't have added any callbacks.