Customize building the node teaser list (front page)

Help me out guys,

I would like to know if there is anyway to override the function where it generates the node teaser list on the front page. I can't even identify where this happens!

what i'm trying to do is:

create 3 columns for the teaser list, but after every row (of 3 teasers), i want to put 3 more custom divs in between. I use for a custom Ajax module where I expand the the full node right there on the front page! (yes this already works fine, tell me if anybody is interested in the code).

But now i face a problem on my site. I know about node.tpl.php, where you can customize every teaser node, but because as far as i know, it is highly cumbersome to try to add something every 3 teaser nodes. It helps if i try to visualize what i'm trying to do abit ...

000 <---- 3 node teasers
-----
___ <---- jQuery magic, those top three nodes expand here! 3 divs of (div class=expandnode-$nid)

000 <---- 3 more teasers
-----
___ <---- 3 divs of (div class=expandnode-$nid)

00 <---- in this example, 2 more last teasers
-----
___ <---- 2 divs of (div class=expandnode-$nid)

After much rummaging around, i managed to find a klunky partial solution, by customizing node.tpl.php and template.php. But the problem with this solution is that I can't get the last 2 divs to show, because it will only flush out the divs after every 3 teasers, and the last row only has 2.

this is my code:

template.php

<?php

function _malayaland_current_col() {
	static $count;
	$count = is_int($count) ? $count : 0;
	$count++;
	if ($count==4) { $count = 1; };
	return $count;
}

function _malayaland_expandnode($op, $nid=0) {
	static $divstr;
	
	switch ($op) {
		case "append":
			$divstr .= "<div id=expandnode-$nid></div>";
			break;
		case "flush":
			$tempdivstr = $divstr;
			$divstr = "";
			return $tempdivstr;
			break;
	}
	
	
}
?>

node.tpl.php

<div class="entry<?php print ($sticky) ? " sticky" : ""; ?>"> 
	<?php if ($page == 0): ?> 
  		<?php 
			$count = _malayaland_current_col();
		?>
		
		<div class="col<?php print $count ?>">
		
		<h2><a href="<?php print $node_url ?>" rel="bookmark" title="Permanent Link to <?php print $title ?>"><?php print $title ?></a></h2> 
  	<?php endif; ?> 
  
	<?php print $content ?>
  
	<?php if ($links): ?> 
  		<p class="info">Posted in <?php print $terms ?> <?php print $links ?></p>
   		<small><?php print $submitted ?></small>
  	<?php endif; ?> 

	<?php if ($page == 0) { print '</div>'; };?>
	
	<?php
		_malayaland_expandnode("append", $node->nid);
		if ($count==3) {
			print _malayaland_expandnode("flush");
		};
	?>
</div>

In fact, not only doesn't this code fully work, but I think this is not the right direction I'm going in. Its very inelegant.

Is there a way to customize the function where it builds this teasers list? Or least tell me where I can find it so that I can copy and build my function instead ...