users last visited blogs array

Hello, I run big multisite blog network with many users in it.

I want to display on some place users 5 last visited blogs.
Of course it is much easier to display it then actually storing it in db.

I came up with code

global $blog_id;
	$current_blog_details = get_blog_details( array( 'blog_id' => $blog_id ) );

	if (is_user_logged_in()) {
	    $user = wp_get_current_user();
	    update_user_meta($user->ID, 'last_visited_blogs',  $current_blog_details->blogname);
	}

it works perfect but saves only last blog.
How to remake this code to save an array of blog names, or even IDs or anything, which later I can convert to blognames and is array of 5 visited blogs.