First ask yourself the question, are you able to use two swf files.

If yes, then you can make an external preloader that you can use for all of your stuff without worrying about making a new one for another project.

If no, you need to slide EVERY frame in your timeline 1 frame forward.

Then you need to find a preloader tutorial and just take the basic components like;

if (loaded){
start the move
}

if(loading){
do nothing but wait
}

if(precentloaded == total blah blah blah){
loaded=true
}

that should be really all of the things you need, go back to one of those "pull out your hair" tutorials and take some of the code.