Adsense Banner after PostID

[JimmyN]

Hi everyone, i have this adsense code here, which workds great the thing is iam trying to get it to show at more posts. Though useing the postcount isnt what i need, becuse if you are on page 6 for example it doesnt show them.

I would like it to show every 4 posts or so (3 banners/text a page max)

So i want to sure on how to change this conditional.
<if condition="!$GLOBALS['FIRSTPOSTID']">

I tryed <if condition="!$GLOBALS['SECONDPOSTID']">

Any ideas? thanks

<if condition="!$GLOBALS['FIRSTPOSTID']">

$spacer_open
<div style="padding:0px 0px $stylevar[cellpadding]px 0px">

<table class="tborder" cellpadding="$stylevar[cellpadding]" cellspacing="$stylevar[cellspacing]" border="0" width="100%" align="center">
<tr>
    <td class="thead" align="left">Sponsored Links</td>
</tr>
<tr>
    <td class="alt1" align="center">
        <adsense code here>
</if>
    </td>
</tr>
</table>

</div>
$spacer_close

</if>