Marketo Engage - Individual Field API Call on Form

For our Marketo Engage, we want to install an API call for one individual question on our demo report. This would hypothetically call to a third party database used as a search engine to identify the exact organization the person key's in. People would begin to type in their organization's name, and it would pop up in the search. They click on it, and then we are able to better prospect them.

Would anyone know how to do this?