HELP please [mx] Simple external jpg preloader?

Please, please don’t be mad and tell me to search the forum for related threads…I’ve been at this ALL DAY and I can’t make it work. I’ve googled, and searched and followed what feels like hundreds of threads, and I’m pulling my hair out! If there’s a thread with a good FLA somebody wants to point me to, that’d be great, but I’d love to see how this works in a living, breathing file…

Here’s what I’ve got and CANNOT make work!

On the first frame of the main timeline, I’ve put my usual preloader, so that I can load the navigation system, which is graphics heavy. Fine. That all works.

On the second frame, I’ve got my “content” movie, which is empty, except for a dynamic text field.

Then also on second frame, I’ve got my navigation system (packed into an MC), with all my buttons.

Then, still on the second frame, I’ve got the following, which I found someplace, and thought I totally understood:

_root.onEnterFrame = function(){
t = _root.content.getBytesTotal();
l = _root.content.getBytesLoaded();
percent = (l/t)*100;
if (t>0 && percent<100) _root.content.percentage = percent;

on the button I’ve used loadMovie just like normal, to load the jpg.

The picture loads fine (slowly), but the preloader doesn’t preload!!

Eventually, I’d like to add a piece of code to fade the .jpg in, but I’ll cross that bridge when I get to it…

Please, please help, and I’m sorry if this is a stupid question, or I’m just missing something obvious…