Creating field with specific required text

Hello,

I am using this plugin for registration for a confidential forum related to health. In addition to having users create a username and password, I also want to have a field where they have to input a specified required password/code that will be given to them by the person who referred them to the site. We want to use it to verify that they were referred by one of our partners. For example, if the common code to register were password1, I want to have a field where that EXACT text has to be entered for the form submission to be received. Is that possible with this plugin?
My form is at http://www.thepozzy.org/registration

Thank you!

http://wordpress.org/plugins/custom-contact-forms/