insert email like a shortcode

hi,

I have next problem, i need to duplicate emails.

On template, i have a additional field
<input type="text" name="extra[email_pr]" value='<?php echo get_post_meta($post->ID, 'email_pr', 1); ?>' style="width: 100%;" />

and if i use contact-form from this post, i need use email from field “email_pr”, how i can do this? Thank you!

P.S Sorry for my english

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