Another UNION ALL query

I have a 'Highlights' heading on my home page.  It is for links to content
on the site ... like specific web pages

I have designed the query below to select the two most popular and least
popular pages used on the site to be the Highlights.  (Each time a web
page is accessed user_hits is increased by 1.)

I would like to display a fifth one that is " ORDER BY RAND () LIMIT 1 "
--- Only I don't know how to ensure it isn't one of the four that are
being displayed already.  Any suggestions?

Ron



SELECT `highlights`.`reference`, `highlights`.`page_command`,
`highlights`.`page_title` FROM (

( SELECT `reference`, `page_command`, `page_title` FROM `user_pages` WHERE
 `include_in_highlights` =1 ORDER BY `user_hits` DESC LIMIT 2 )

UNION ALL

( SELECT `reference`, `page_command`, `page_title` FROM `user_pages` WHERE
 `include_in_highlights` =1 ORDER BY `user_hits` ASC LIMIT 2 )

) AS highlights ORDER BY `highlights`.`page_title` ASC