[Plugin: List category posts] sort posts alphabetically by a custom field name

I was hoping to use this plugin to sort posts on a category page (“Artists”) alphabetically by a custom field name without changing the template(s).
The posts are titled by the name of each artist: e.g., “Sue Smith”, “Paul Alan Jones”. First I looked for some way to sort the posts alphabetically by the last word in the post title. Can’t find that.

So, my next idea is to put a custom field on each post called last_name (custom field text values for the above examples would be “Smith, S” and “Jones, P”) and to use this plugin to simply display the post titles sorted in alphabetical order by last name (using the custom field) and displayed as the artists’ names as they appear in the title “first last”).

So the display would just be a list names (with underlying links to the post that shows the artist’s bio & some images of art)
Paul Alan Jones
Sue Smith
How would I format the shortcode to sort by the custom field “last_name” in alphabetical order? Thanks

http://wordpress.org/extend/plugins/list-category-posts/