R – How to control main timeline from external swf

You need to add an event listener o the loader first so that you know when the load is complete. So from your code snippet i would suggest something like

var request:URLRequest = new URLRequest(file);
loader.addEventListener(Event.COMPLETE, function(event : Event) : void
{
var swfTimeline:MovieClip = loader.content as MovieClip;
swfTimeline.nextFrame();
});
loader.load(request);

Lots of different ways to organise this code but that should do the trick

What you want to do is definitely possible. You need to wait until the SWF is loaded before you can tell it to go to a specific frame. The easiest way to do this is using the MovieClipLoader class.

var loader:MovieClipLoader = new MovieClipLoader();
loader.addListener(this);

function onLoadComplete(loadedClip) {
    loadedClip.gotoAndStop(5);
}

loader.loadClip("floorplan.swf", targetClip);

That will load floorplan.swf into the placeholder named "targetClip" and, once it's loaded, have to jump to frame 5.

For more info, see the MovieClipLoader documentation: http://livedocs.adobe.com/flash/9.0/main/wwhelp/wwhimpl/js/html/wwhelp.htm?href=00001993.html