OK, obviously you need a workaround, my proposal.

If you have the sourcecode for the loaded swf-files

write down all the totalframes length (if you have multiple scenes, sum them up)

then for the play progressbar write an enter_frame event that gets the percentage of your loaded movie

for example: you have a movie with 1000 frames and a framerate of 25 (=40 seconds of animation)

that is loaded in your 30 fps main movie.

You won´t be able to influence the running time (it will only run 33 seconds) but you will be able to set the progressbar according to the percentage of the loaded movieclip, so instead of saying gotoAndPlay(framenumber),

you must set the progressbar dimension to the _totalframes property of your loaded movie,

then in the enter_frame function you get the position of the movie via _currentframe and set the position of the

progressbar-knob (or whatever you`re using) to the percentage of the time the movie has played

it will look similar to that

_root.on(enterFrame){

     getProgress();

}

function getProgress():void{

   myPb.knob._x = myPb._width * (loadedMovie._currentframe/loadedMovie._totalframes);

}

for the ProgressKnob, that the user can drag to get to aposition within the loaded mc use a setter like

dragKnob.on(MouseDrag){

   setProgress();

}

function setProgress():void{

  var position:Number =  myPb.knob;

  var totalLength = myPb._width;

  var percentage:Number = position/totalLength;

   loadedMovie.gotoAndPlay(Math.round(percentage*loadedMovie._totalframe s));

}

Problem could be, that the EnterFrame function could block the setProgress function (may be you should get the progress only every 20 frames or so)

(Another reason to switch to AS3)