problem with hook

[chack1172]

Hi guys I'm making a plugin and I have a problem with hook, this is the code:

$plugins->add_hook("build_forumbits_forum", "ficon_icon");

function ficon_icon() {
    global $forum, $ficon, $templates;

    if($forum['icon_url'] != "") {
        eval('$ficon = "'.$templates->get('ficon_index').'";');
    } else {
        $ficon = "<small>Forum Icon</small>";
    }
}

It don't show me any error and don't show me template or text "Forum Icon", how I can fix it?