Manipulate Head based on CMS block

Question

I have a block which I can call by using the following in a CMS page's content:

{{block type="karl_catalog/supplier_product" supplier_id="1242" template="karl_catalog/supplier_product.phtml"}}

This gets a collection of products and spits them out of the page and is all working fine.

However, I am trying to use an observer to see when this is called as I need to add rel="next" and rel="prev" links to the header. I've tried using the controller_action_layout_generate_blocks_after observer, but I've been unable to find a way to determine if the block type matches the above block type (above).

$l = $observer->getEvent()->getLayout();
foreach ($l->getAllBlocks() as $block) {
    echo $block->getType();
}

The above code echo's the block types, but karl_catalog/supplier_product is not shown.

Any ideas how I can achieve this?