Previous/Next links or buttons in Custom Post Type

Hi,
I was wondering if there's a way to change the name of the link to "PREVIOUS" or "NEXT" on the pagination of a Custom Post Type. I'm using this filter:

add_action( 'generate_after_entry_content', 'tu_custom_post_type_post_nav' );
function tu_custom_post_type_post_nav() {
if ( 'transactions' == get_post_type() ) : ?>
<footer class="entry-meta">
<?php generate_content_nav( 'nav-below' ); ?>
</footer><!-- .entry-meta -->
<?php endif;
}

Thanks!

Jon