exclude forum in ad code

[NarutoFTW]

Can someone help me edit the code below to allow me to exclude certain forums? Like exclude forum id: 301.

<vb:if condition="$post['isfirstshown']">
<li class="firstpost_advert_container"><div class="firstpost_advert">

<script type="text/javascript">
    google_ad_client = "ca-pub-6546546546546";
    google_ad_slot = "6401555550";
    google_ad_width = 728;
    google_ad_height = 90;
</script>
<!-- 728x90, created 8/7/09 -->
<script type="text/javascript"
src="//pagead2.googlesyndication.com/pagead/show_ads.js">
</script>

</li>
</vb:if>

Thanks a lot guys.