WordPess identify last post in the loop, Tested Code
<?php
/* If you want to change the last post on each page:
http://return-true.com/change-the-last-post-in-the-loop-in-wordpress/
*/
if(($wp_query->current_post + 1) == $wp_query->post_count) {
//Whatever you want to occur should this be the last post of the current page
}
?>