Ad after every sixth post

[kodbg]

Hello
I want to put an ad after every 6 post, to be shown only if the split page has 9 posts.
This code:

<vb:if condition="$post[postcount] % $vboptions[maxposts] == 6 AND $GLOBALS[threadinfo][replycount] > 8">

works OK, but only for first page.
If i split my pages on every 20 posts and the thread has 27 posts, the ad will be shown on second page. But on second split page are only 7 posts - i don't want to show it.


Please, help with code.