I cannot get the callback to work at all when I got in touch with worldpay they said it is because the https:// isn't on the url
I think it has to be edited here but don't know how
tep_draw_hidden_field('MC_callback', substr(tep_href_link('ext/modules/payment/worldpay/junior_callback.php', '', 'NONSSL', false, false), strpos(tep_href_link('ext/modules/payment/worldpay/junior_callback.php', '', 'NONSSL', false, false), '://')+3));