shortcode to pull email addresses from one form

// http://www.gravityhelp.com/forums/topic/collecting-email-addresses
// shortcode usage: [submitted_emails form='FORMID']
add_shortcode('submitted_emails', 'retrieve_emails');
function retrieve_emails($emails) {
        $form_id = $emails['form'];
    // get all the field values for one form and one field ID
        $addresses = RGFormsModel::get_leads($form_id, 'CHANGE THIS TO YOUR EMAIL FIELD ID', 'ASC');
    // initialize the HTML we are going to return
        $html = "<ul class='email_addresses'>\n";
    // loop through all the leads
        foreach ($addresses as $email) {
                $html .= "\t<li>$email</li>\n";
        }
        $html .= '</ul>';
    // return the list
        return $html;
}