wrap-amr-users.php

<?php
/*
Plugin Name: Wrap amr-users in div
*/
if ( function_exists( 'amr_userlist' ) ) {
        remove_shortcode( 'userlist' );
        add_shortcode( 'userlist' , 'css_amr_userlist' );
}
function css_amr_userlist( $att ) {
        $html = '<div class="amr-userlist"><!-- wrap amr_userlist in div -->';
        if ( function_exists( 'amr_userlist' ) ) $html .= amr_userlist( $att );
        $html .= '</div><!-- /wrap amr_userlist in div -->';
        return $html;
}