[jQuery] How can we stop the "animate" function?

[sundowatch]

I wonna stop an animate function which hasn't been completed yet.

For example;

<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript">

$(document).ready(function(){

$("div#button1").click(function(){
$("#box").animate({
"margin-left" : "150px"
});
});
$("div#button2").click(function(){
$("#box").animate({
"width" : "500px"
});
});

});

</script>

I started button1 animation, If I click "button2","box" must stop
animate1 and start animate2.
How can I do this?