help with simple play/pause button

[Actionscriptkills]

I'm trying to make a single button both stop and play the movie. (I'm using setInterval to pause the movie at various points.) I'm trying to learn actionscript, so please excuse any terrible errors. (simple example file attached)

First frame of movie:

function pause(){
play();
clearInterval(timer);
}
playing=true;

if (playing=true){
playing!=false;
}
else if (playing!=true){
playing=false;
}

On the button:

on (release, keyPress "<Space>"){
clearInterval(timer);
if (playing=true){
stop();
playing!=true;
}
else if (playing=false){
play();
}
}