How to use filefield in a compound field?

Hello,

I'm trying to create a CCK compound field with a file upload. I'm able to get the default file upload to show on the widget with:

	$element['corevideofield']['files']['new'] = array(
		'#type' => 'file',
		'#title' => t('or upload a new video'),
		'#default_value' => array(),
	);

But if I change the #type to 'filefield' I get no output at all. I assume I'm missing something, if you could point me in the right direction it would be greatly appreciated.

[edit]
I've found I can make the field appear by using:

     $elements['corevideofile']['files']['new'] = filefield_elements();

but there's a few php warnings and it's non functional. I'm not sure if I'm getting closer or if this is a red herring...