[SEOvB]

<!-- message -->

                <div id="post_message_$post[postid]" class="post_message">
<if condition="(($post[postcount] % $vboptions[maxposts] == 1))">
         <div style="float: right; margin: 3px; padding 3px;">PLACE AD CODE HERE
</div>
</if>
$post[message]</div>
                <!-- / message -->

After

		$template_hook[postbit_signature_start]

add

		<div style="clear: both; height: 5%; border-width: 1px 0 0 0; border-style: solid; border-color: black; vertical-align: middle; padding: 5; margin: 5;"><br />

Then after

<!-- / controls -->

Add

</div>

Demo I've changed my CSS slightly from whats posted above, but this is the effect that it will give.