public function updateAction(){

    $block = $this->getLayout()->createBlock(
        'Mage_Core_Block_Template',
        'namespace_update_form_head_data',
        array(
            'template' => 'namespace/update/head/data.phtml'
        )
    );

    /**
     * @var Mage_Adminhtml_Block_Page_Head
     */
    $head =$this->getLayout()->getBlock('head');
    $head->append($block);
}

<?php echo $this->getChildHtml('namespace_update_form_head_data') ?>