orderby meta_value that's serialised

I’m trying to order some posts so taht they’re ordered by price.

I’m using a theme. The way this theme works, is that the price has been serialised in a field called ‘key’.

So, my query_posts looks like this:
query_posts('showposts=' . $limit . '&paged=' . $paged . '&cat='.$cat . '&meta_key=key' . '&orderby=meta_value_number' . '&order=ASC');

Only problem is, that I need to be able to expand on meta_key=key. I almost need to say something like meta_key=key[‘price’] – but obviously that doesn’t work.

Seriously, if anyone can help – they’ll gain legendary status.

Thanks