function submitForm() {

        var strZipCode = document.menuForm.ZipCode.value;
                                        
        if ((strZipCode == "") || (isNaN(strZipCode)) || (strZipCode < 0 || strZipCode.length != 5) || (strZipCode.indexOf(".") != -1)) {
            window.location = "/";
        }
        else {
            document.menuForm.submit();  
        }
}