If i understand your correction correctly you want to make it where if you lose focus on your listbox that it disappears correct?
Try the code below. Im assuming you have basic understanding of jquery/can call jquery.
<html>
<head>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
<script type="text/javascript">
$(document).ready(function(){
$("#IdOfYourListBox").live("blur", function(){
$("#IdOfYourListBox").hide();
});
});
</script>
</head>