wordpress menu problem

we are want to pass value in url when we click om menu in
<?php wp_nav_menuservice(array(‘menu’ => ’27’)); ?>
function
click on menu , current output in url:
http://localhost/daffodilsite/?page_id=540
and we want in url:
http://localhost/daffodilsite/?page_id=540&cityid=3

please help me how to pass cityid in url

thanks
Rajeev Dhar