[Jon]

I'd highly recommend upgrading to CDSEO Pro:
http://www.x-cart-seo.com/cdseo-pro-for-x-cart/cdseo-basic-vs-pro.php

This should work:

$qry_string = func_qs_remove($QUERY_STRING, "js");
if ($qry_string)
    $qry_string .= "&";

// WebsiteCM - CDSEO Compatible
$wcm_url = str_replace('?' . $QUERY_STRING,'',$_SERVER['REQUEST_URI']);
$js_update_link = $wcm_url . "?" . $qry_string . "js=" . ($js_enabled == "Y" ? "n" : "y");
unset($qry_string);