Ok, real stupid while writing this post I was thinking about first looping of the menu items and then storing them in an array for later use. With the example on the following page I can manage that:
http://codex.wordpress.org/Function_Reference/wp_get_nav_menu_items
// Get the nav menu based on $menu_name (same as 'theme_location' or 'menu' arg to wp_nav_menu)
// This code based on wp_nav_menu's code to get Menu ID from menu slug
$menu_name = 'custom_menu_slug';
if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $menu_name ] ) ) {
$menu = wp_get_nav_menu_object( $locations[ $menu_name ] );
$menu_items = wp_get_nav_menu_items($menu->term_id);
$menu_list = '<ul id="menu-' . $menu_name . '">';
foreach ( (array) $menu_items as $key => $menu_item ) {
$title = $menu_item->title;
$url = $menu_item->url;
$menu_list .= '<li><a href="' . $url . '">' . $title . '</a></li>';
}
$menu_list .= '</ul>';
} else {
$menu_list = '<ul><li>Menu "' . $menu_name . '" not defined.</li></ul>';
}
// $menu_list now ready to output
echo $menu_list
The code above just needs some adapting but it will do! :)