you can use a script like this:
on (rollOver) {
_root.createEmptyMovieClip("emptyMC", 2);
_root.emptyMC.loadMovie("external.swf");
_root.emptyMC._x = 145;
_root.emptyMC._y = 120;
}
It will create a empty movie clip at those x and y cordinates and load your external swf into that empty movieclip.