It works! Once again you’ve come to the rescue – thanks so much, your help is really appreciated.
For anyone else looking to do the same thing, here is the shortcode I ended up with. Needed to add the meta_key to the above code.
Note the meta_key is the name of the Custom Field, in my case it was event_id.
[wp_show_posts id=”16″ settings=”meta_key=event_id&orderby=meta_value&order=ASC”]