[Plugin: Contact Form 7] check box for reader to get copy emailed to him/her

In case you need it, my blog is at gardenofshadows.ca. I would really like to create a checkbox option allowing a reader to check the box if they would like a copy of the email to be sent to him/her as well when they send me a message via Contact Form 7.

I can’t find anything anywhere, not in the FAQs, not in this forum, not by Googling, advising how to do this.

Is it possible? If, how? If not, would you consider adding this option to a future version of Contact Form 7? I’ve seen this on other WordPress blogs but I don’t know what plugin is being used.

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