Pass form field in url

Hi.
On submission of the form I want to pass a field value in the url. In ‘additional settings’ I want to add the redirect url along with the field value. Any ideas how to do this? Many thanks

Here’s an example of how I would like it to work

Additional Settings:
on_sent_ok: “location.replace(http://www.myurl.com?myVariable=%5Bfield-name%5D’);”

http://wordpress.org/plugins/contact-form-7/