Pass form data submission on to 2nd and 3rd form

This should be simple for anyone that understands form submission and passing on data. I want someone to help me code a way to pass on user data collecting in a form to a 2nd and 3rd form in a checkout process. I am able to add html to each form... but the form is hosted on a 3rd party shopping cart service. I am attaching an easy-to-understand word document that explains with pictures what I am trying to do. If this goes well, I have several other projects. ## Deliverables See the word doc for the details