Wordpress URL rewrite with custom $_GET variable
===

I'm looking for a way to rewrite a URL similar to wordpress where:

    http://www.example.com/?p=5
becomes

    http://www.example.com/some-page-with-that-title
I'd like 

    http://www.example.com/events/?event_id=23

to become

    http://www.example.com/events/some-event-title

I've discovered the wordpress rewrite api and have successfully gotten the following to rewrite the url using and events template page.


    add_action( 'init', 'events_permalinks' );
    function events_permalinks() {
        add_rewrite_rule(
            'events/([^/]+)/?',
            'index.php?pagename=events&event_name=$matches[1]',
            'top'
    );
    }

    add_filter( 'query_vars', 'events_query_vars' );
    function events_query_vars( $query_vars ) {
        $query_vars[] = 'event_name';
        return $query_vars;
    }
And get the variable with
get_query_var( 'event_name' )

I know I need to look up the event_id in the non-wordpress events table to get the name but I'm not sure where to put the query so I can swap it into the url. Hopefully I haven't confused things. :)