Broken query

I am trying to write a query to select a trivia question, but I don't want
the trivia question category to be the same two days in a row so I added a
second "SELECT" syntax to find out what category was used yesterday.  This
works when I test it "live", but doesn't work when it is part of a cron
job.  How do I get the value of `Bible_trivia_category_reference` from the
second SELECT query to be used in the first?  What change is needed?  Ron

SELECT * FROM `verse_of_the_day_Bible_trivia` WHERE `assigned_date` =
'0000-00-00' AND `seasonal_use` = $bible_trivia_application AND `live` =1
AND NOT `Bible_trivia_category_reference` = ( SELECT
`Bible_trivia_category_reference` FROM `verse_of_the_day_Bible_trivia`
WHERE `assigned_date` = '$last_mailing_date' LIMIT 1 ) ORDER BY RAND()
LIMIT 1