password protecting custom fields

hi there,

the thumbnails on this page are a custom field. the page is password protected, but as you can see, the password protection is not working on the custom field: http://kakadunativeplants.com.au/recent-projects

how can i password protect the custom field too?

i found this piece of code on a blog, but i don’t know where to place it within my page template php code (i’ve tried a few different spots, but nothing has worked):

<?php
if ( !post_password_required() ) {
echo ‘protected stuff’;
}
?>

thanks!