Contact Form 7 Redirect link breaking

I used the on_sent_ok method on this page (http://contactform7.com/2010/03/27/redirecting-to-another-url-after-submissions/) to create a redirect after form submission and it’s working great except for one thing – the destination link has a & in it and it gets converted to & somehow, and the link breaks. Is there anything I can do to combat this?

Thanks!