Transition effects

I know most of you have probably sen a question about transitions a million times, but heres another one.

I am new to loading external swf files, only ever done it once before, and it was alot simpler! basically, i have a site i am designing, and the navigation are movie clip buttons.

I am using code i found on a tutorial, which is below

//stop this timeline
stop();
//hide the preloader
preloaderGraphics._visible=false;
//initialise a variable
nextMovie="content1.swf";
//load the starting movie into level 1
loadMovieNum(nextMovie,1);
//button1 actions
button1.onRelease=function(){
 //this makes sure that content 1 isn't already loaded
 if(nextMovie!="content1.swf"){
 //set the variable that holds the name of the movie to be loaded
 nextMovie="content1.swf";
 //tell the currently loaded content movie to play it's outro animation
 _level1.gotoAndPlay("outro");
}
}
//button2 actions
button2.onRelease=function(){
 //this makes sure that content 1 isn't already loaded
 if(nextMovie!="content2.swf"){
 //set the variable that holds the name of the movie to be loaded
 nextMovie="content2.swf";
 //tell the currently loaded content movie to play it's outro animation
 _level1.gotoAndPlay("outro");
}
}
//button3 actions
button3.onRelease=function(){
 //this makes sure that content 3 isn't already loaded
 if(nextMovie!="content3.swf"){
 //set the variable that holds the name of the movie to be loaded
 nextMovie="content3.swf";
 //tell the currently loaded content movie to play it's outro animation
 _level1.gotoAndPlay("outro");
}
}

Ok… this i all understand, i was a programmer by trade before and am moving into flash now.

However, when i change the instance of the movie clips to button1 etc, the movie for the button wont play, when i change the button instance then it doesnt work…

BASICALLY… to wrap it up, i cant get it to work, and i am wondering if i have to rename something for movie clips to make it work.

This may be a realy thick question and i hope someone can clear it up for me so i can get through this website without pulling my hair out!

Thanks!