Updating the value of hidden fields based on page properties

Hi, 

For one of my customers they want to be able to add a series of properties to a page, and then when a form is included on the page, the hidden values are added to a series of hidden fields (This is essentially so that they can have one form used on thousands of pages, and not need 1000s of identical forms with different hidden values), has anyone ever done anything like this?

Thanks in advance

Andy