Link Entry-Title to Custom Meta Data in Post List Grid

I’d like to make the entry-tile linkable on my post lists.

This is the code I am using to make it link to meta-data found in the post:

add_filter('tc_grid_display_figcaption_content' , 'tc_grid_set_expanded_post_title');
function tc_grid_set_expanded_post_title( $_html ){
          if ( ! $this -> tc_force_current_post_expansion() )
              return $_html;
          global $post;
          $_title = apply_filters( 'tc_grid_expanded_title' , $post->post_title );
          $_title = apply_filters( 'tc_the_title'           , $_title );
          $_title = apply_filters( 'tc_grid_expanded_title_html';
	  $linkvalue = get_post_meta($post->ID, 'affiliate_link', true);

	  if($linkvalue) {
          sprintf('<h2 class="entry-title"><a href="' . $linkvalue . '" rel="bookmark">%1$s</a></h2>',
              $_title
          ) );
          }

	else {
          sprintf('<h2 class="entry-title">%1$s</h2>',
              $_title
          ) );
        }
          return $_html . $_title;
        }

It doesn’t work. ??