Problem with ORDER BY in wp_query

Hi
I’m looking for solution for a long time but I can’t find it – maybe you can help..

My query is:

$qq = new WP_Query(array(
		'post__in' => array(940, 939, 941),'showposts' => 4, 'nopaging' => 0, 'post_status' => 'publish', 'ignore_sticky_posts' => 1, 'post_type' => array( 'post', 'portfolioentry')
		));

I’m trying to display posts in post id order: 940, 939, 941.

I’m trying to use meta_vaue_num [http://codex.wordpress.org/Class_Reference/WP_Query#Order_.26_Orderby_Parameters] but without success.

Please help. Thanks in advance!
Rafal