I tested it but it difficult to implement it in VWR because of JSON call back. So it cannot be done VWR using a form field method.
But I studied the site's behavior that I found out that you can actually get them using the websites API by construction how the website do it. Here, is the JSON response once you select the Comune "ARGENTO",
and by using the Zip code form that response, you can build the results API in JSON format,