Specify Popup LEFT And TOP window Position

[monie]

<SCRIPT language="JavaScript">
<!-- Hide the script from old browsers --
function surfto(form) {
var myindex=form.dest.selectedIndex
window.open(form.dest.options[myindex].value,"main","height=500,width=500,location=no," + "scrollbars=no,menubars=no,toolbars=no,resizable=yes");
}
//-->
</SCRIPT>

this is my coding for drop down popup menu...
it only specify the width and the height of my popup window!

ANYONE CAN HELP ME ADD EXTRA LINE INSIDE THE CODE TO SPECIFY THE LEFT AND TOP OF THE POPUP PAGE?
IT LOOKS SOMETHING LIKE THIS...

",left=" + l + ",top=" + t + "