求助

初学者写了一段代码来实现两个div相遇时停止的问题，但一直没能实现停止，请大神们看一下，帮忙改正。
<script type="text/javascript">
var div_1=document.createElement("div")
div_1.style.position="absolute";
div_1.style.top="200px";
div_1.style.left="200px";
div_1.style.width="20px";
div_1.style.height="20px";
div_1.style.border="solid 1px #F00";
div_1.style.backgroundColor="#F00";
document.body.appendChild(div_1);
var div_2=document.createElement("div")
div_2.style.position="absolute";
div_2.style.top="200px";
div_2.style.left="700px";
div_2.style.width="20px";
div_2.style.height="20px";
div_2.style.border="solid 1px #F00";
div_2.style.backgroundColor="#F00";
document.body.appendChild(div_2);
var mytimeout;
var mystop;
var new_left1=parseInt(div_1.style.left);
var new_left2=parseInt(div_2.style.left);
mytimeout=window.setTimeout("move()",100)
function move()
{
new_left1=new_left1+10;
new_left2=new_left2-10;
div_1.style.left=new_left1+*px*;
div_2.style.left=new_left2+*px*;
mytimeout=window.setTimeout("move()",100)
}
function mystop()
{
when(new_left1+20+1==new_left2)
{
window.clearTimeout(mytimeout);
div_1.style.left=new_left1+*px*;
div_2.style.left=new_left2+*px*;
}
}
</script>