Exclude some pages from horizontal header menu

Hey there!
I want to hide some of my pages from the horizontal menu beow the header image. I already sorted out the page IDs
Do I exclude them with this function? Where to add?

// Exclude specific pages in wp_page_menu
if( !function_exists( 'mytheme_page_exclude' ) ) :
function mytheme_page_exclude( $args ) {
	$args['exclude'] = '80';
	return $args;
}
endif;
add_filter( 'wp_page_menu_args', 'mytheme_page_exclude' );

Unfortunately I cannot give you a link to the site b/c its not online yet.