Simple Multi-Part Form to work with API

We need a multi-part form to work with our API. On submission of part 1, our system returns XML data. On submission of part 2, our system returns XML data. On submission of part 3, our system returns XML data. This form will be web based and embedded into a site. Who has a quick solution? I have attached a detailed sample of exactly what happens. I will NOT be providing you with the API key. We will work together to ensure everything works properly. See attachment. Indicate that you have reviewed the attachment and understand what we are looking for when you bid.