Scusate ho risolto da solo posizionando un cue point e mettendo in pausa il filmato:


red_btn.onRelease = function() {
attachMovie("FLVPlayback","myVideo_mc",1);
myVideo_mc.contentPath = "miovideo.flv";
myVideo_mc._x = 0;
myVideo_mc._y = 20;
myVideo_mc._height = 480;
myVideo_mc._width = 640;


var cuePt:Object = new Object(); //create cue point object
cuePt.time = 0.899;
cuePt.name = "FineFilmato";
cuePt.type = "actionscript";
myVideo_mc.addASCuePoint(cuePt); //add AS cue point
// add 2nd AS cue point using time and name parameters
myVideo_mc.addASCuePoint(5, "FineFilmato");


var listenerObject:Object = new Object();
listenerObject.cuePoint = function(eventObject:Object):Void {
trace("Elapsed time in seconds: " + myVideo_mc.playheadTime);
trace("Cue point name is: " + eventObject.info.name);
trace("Cue point type is: " + eventObject.info.type);
myVideo_mc.pause();
}
myVideo_mc.addEventListener("cuePoint", listenerObject);