[Michael Adams (mdawaffe)]

function my_get_forum_link_filter( $link ) {

$link = 'yay'; // Whatever you want to do with the link

return $link; // Very important line!

}



add_filter( 'get_forum_link', 'my_get_forum_link_filter' );

That last line adds your custom filter function to the get_forum_link filters.