[FrankP]

Many thanks to Mystics from vb-germany.com. He gave me the following code for the postbit_legacy and this one is working like a charme:

<vb:if condition="THIS_SCRIPT == 'showthread' AND (($post['postcount'] % 15 == 10) OR $post['postcount'] == 10)">
	<div class="thread_controls">
		<div style="width: 100%; text-align: center">
			<!--@vbbanners:3@-->
		</div>
	</div>
<vb:elseif condition="THIS_SCRIPT == 'showthread' AND (($post['postcount'] % 15 == 5) OR $post['postcount'] == 5)" />
	<div class="thread_controls">
		<div style="width: 100%; text-align: center">
			<!--@vbbanners:2@-->
		</div>
	</div>
</vb:if>