wp_fun95 on "[Plugin: Contact Form DB] Preventing duplicate e-mail addresses in database"

Hi Michael,
I have the same problem with duplicate emails. I have tried your suggested solution under: http://cfdbplugin.com/?page_id=904
but I encounter a very specific problem due to the WP theme I use.
I use the http://www.pagelines.com theme (free version) which does not allow changes in the functions.php as this is considered changing of core fields not supported by this theme.
I asked support from them but they threw the ball to the plugin author's support. So, if you have any ideas how to cope with this, I would greatly appreciate.
many thanks in advance
BTW, I love your plugin, it is just great!