sorry but thi is only a Javascript request and i dont now the Javascript that you are use... )o:
try this... (o:
<script type="text/JavaScript">
<!--
function MM_openBrWindow(theURL,winName,features) { //v2.0
window.open(theURL,winName,features);
}
//-->
</script>
<a href="#" onclick="MM_openBrWindow('{media_src}','{image_name}','toolbar=yes,location=yes,status=yes,menubar=yes,scrollbars=yes,resizable=yes,width=100,height=100')">{thumbnail}</a>