Hi , I have just written a simple bit of JavaScript to create Parcel tracking , but it is erroring when i insert it into Zen-cart

It works fine as a standalone html page on the same server , but as soon as I add the script into HTML_Header it errors on page with IE7 giving the error : Object Expected

Code:
<script language="javascript" type="text/javascript" runat="server">
function goTrackit2(){
            var target = 'http://www.interlinkexpress.com/service/tracking?consignment=' + document.getElementById('consignment2').value;
            if (document.getElementById('consignment2').value != "")
            {
                        document.form1.action = 'http://www.interlinkexpress.com/service/tracking?consignment=' + document.getElementById('consignment2').value;
                        document.form1.submit();
            }
            else
            {
                        alert("You didn't type in a tracking number");
            }
}

</script>
It still works fine , but with an IE error , its going to put people off my site.
It works fine with no errors in firefox ( i love FF ! )


Any guru's out there give me any clues ?