problem with menu

hi, plz help me with menu. I want to create menu with table but default is ul/li. i read codex and find fucntions which build menu.

$menu = wp_get_nav_menu_object( $locations[ 'Primary' ] );

    $menu_items = wp_get_nav_menu_items($menu->term_id);

    $menu_list = '<table width="700px" id="menu-' . $menu_name . '"><tr>';

    foreach ( (array) $menu_items as $key => $menu_item ) {
        $title = $menu_item->title;
        $url = $menu_item->url;
        $menu_list .= '<td><a href="' . $url . '">' . $title . '</a></td>';
    }
    $menu_list .= '</tr></table>';

echo $menu_list;

but its not work. i dont know who get $menu->term_id, but if i use this code
wp_nav_menu( array('echo'=>'false', 'sort_column' => 'menu_order', 'container_class' => 'menu', 'theme_location' => 'Primary' ));
it is work. Have u any idea how do it ?