[SOLVED] Add css code in additional.css Template by plugin

[omardealo]

i want add css code in additional.css Template , but my code dose not work

hook : parse_templates
code :

$csscode = '.threadlisthead span.threadinfo {
    width: 48%;
}
.threadbit .threadinfo {
    width: 48%;
}';  
$vbulletin->templatecache['additional.css'] .= '$csscode';