——————————————-//
onClipEvent (load) {
Max = 3;
Sec = 3;
Path = “/img/”;
n = depth=cnt=0;
function loadPic() {
n++;
if (n>Max) {
n = 1;
}
depth++;
mcName = “mc”+depth;
this.attachMovie(“pic”, mcName, depth);
this[mcName].loadMC.Loaded = false;
this[mcName].loadMC.loadMovie(Path+”pic”+n+”.jpg”);
if (depth>2) {
this["mc"+(depth-2)].removeMovieClip();
}
}
loadPic();
}
onClipEvent (enterFrame) {
cnt++;
if (cnt>Sec*24) {
cnt = 0;
loadPic();
}
}

書き込む場所はmotiontween.flaのムービークリップmy_mc内にフレームアクションを書くと手軽にできるかと思いますよ。
// my_mc内の1フレーム目に記述
var loader:URLLoader = new URLLoader();
loader.addEventListener(Event.COMPLETE, onComplete);
loader.load(new URLRequest(“test.txt”));

function onComplete (event:Event)
{
my_txt.text = event.target.data;
}