multi-step form

I'm using the Captcha module in a multi-step form that contains two steps; the Captcha field resides on the second step.
When I hit "Previous" button to navigate to the first step and then go back to the second step of the form, the captcha field disappears.
Can you please advice me how to keep the captcha field all the time on the second step ? I'm not a Drupal programmer, so if someone could share some sample code, it would be great.
Here are the most important methods from the code I'm using:

<?php
function multistep_form($form, &$form_state) {

I have a multi-step form that is a job application.

On one step the applicant enters information for professional references, and on another, character references. They may add multiple references (field groups) on each page. The field groups for both types of reference include an email field, and a hidden "email sent" field.

At the end of the form, when the applicant submits the form, I wish to send customized emails to each of the references, and populate the "email sent" field with "yes".