How to create a custom menu
Ok I found what was wrong :
I needed to register the function in the template.php :

function business_theme_registry_alter(&amp;$theme_registry) {
    $theme_registry['menu_tree__menu_block__menu_navbar']['function'] = 'business_menu_link__menu_block__menu_navbar';
}
function business_menu_link__menu_block__menu_navbar($variables) {

}