Flex. Calling methods on embedded movieclip

I have a flex application that makes use of an animated throbber (loading graphic) that I created in flash cs3. The throbber is embedded in the flex app at compile time and implemented through an mx:Image component. I simply want to be able to stop the animation of the embedded movieclip. I thought throbber.stop() would do it (throbber is the ID of my mx:Image component). I was wrong. This seems to only work with dynamically loaded swfs. Does anyone know how to call methods on embedded movieclips? Thanks in advance.