Animation Controls within AS3 Transitions? Is this possible?

I created a multimedia Flash file (cartoons, photos, sound included), and to run the animation, my team created some simple buttons (stop, play). We have some complex Actionscript running portions of our animation, including the fl.transitions.easing classes and a playInterval sequence. As a result, it seems that our play buttons do not work within the easing transitions or the playInterval. (For instance, when i hit the stop button during a photo transition, the animation only pauses once the transition is over.)

I have not found anything in the AS3 books explaining how to integrate playbutton controls with easing and the playInterval functions. Is this possible?

I guess we could simply export our animation to YouTube and use the YouTube player controls, but I cannot find a good format for this, or a free software that will convert the fla file into a YouTube acceptable format. Any/all advice very welcome!!!