Hi,
I was wondering what the best option for the following would be - I am in the process of putting a site up (on trial) and wanted the ability for a form (or document) to pop-up on checkout (before payment) if a particular product (or product from a specific category) exists in the cart -
i.e. the buyer wants to purchase? It's a sort of a disclaimer form which would need to be submitted with the order - but ONLY IF a specific product from a certain category existed in the cart.
 
Example scenario: buyer wants to purchase a restricted item (such as tobacco) amongst his other purchases, at checkout, a form would be needed to certify / verify that the buyer is above the legal age, etc. and when the form is filled in - it is submitted together with the order being placed and payment taken.