Is there a way the add the prev next buttons to the product info pages?

I tried to edit the main page template with this code:

<!--bof Prev/Next top position -->
<?php if (PRODUCT_INFO_PREVIOUS_NEXT == 1 or PRODUCT_INFO_PREVIOUS_NEXT == 3) { ?>
<?php
/**
* display the product previous/next helper
*/
require($template->get_template_dir('/tpl_products_next_previous.php',DIR_WS_TEMPLATE, $current_page_base,'templates'). '/tpl_products_next_previous.php'); ?>
<?php } ?>
<!--eof Prev/Next top position-->
And it didnt work :-(