I would like to be able to control a flash movie stream using JavaScript in the same pages as the flash component including:
The SWF needs to expose functions to Javascript using the ExternalInterface API from the Flash libraries. This allows Javascript to call into Flash and vice-versa.
http://livedocs.adobe.com/flex/3/langref/flash/external/ExternalInterface.html
"Is this possible without modifying the SWF that is currently used to play the movie" .. it's only possible if the SWF you are using implements the ExternalInterface with documented functions suitable to your needs - as described by cliff.meyers ... otherwise, .... no