I am using the following code in Wordpress to query events (custom post type) and order them by date chronologically..

query_posts( array( 'post_type' => 'events', 'showposts' => 10, 'orderby' => 'meta_value_num','meta_key' => '_ecmb_datetime' ) );

Where the meta key _ecmb_datetime is, this is the timestamp of the event.

I don't want to show events that have already happened, so my question is how do I only show events happening after my current time, and how do I sort reverse chronologically?

Any help is greatly appreciated