Include comments form in edit.php

I’m writing a CRM plugin for WordPress and I’d love to use the built-in comment form within my custom post type edit page (through the admin); to make it truly functional for its purpose I have to add at least one custom field to the form. I can’t find a tut or hack to point me in the right direction on it. Anyone know how to easily add fields to the admin comment meta box? Please note I want to modify the box in edit.php, NOT edit-comments.php.

Thanks!