I am creating a webshop, using commerce module. I set up, that if a customer wants to pay his items, the VAT (27%, based on the Hungarian laws) is added to the end of the list and the final amount is accumulated with the amount of VAT. Also the module commerce_eu_vat is installed and there is a field under the billing and shipping informations, where the customer can type in the EU VAT number. The provided EU VAT number is beeing checked with the webpage: http://ec.europa.eu/taxation_customs/vies/ .
I would like to do, that if the EU VAT number is valid and it is not from Hungary (i.e.: the VAT number doesn't start by HU), then the amount of VAT would be 0% and in any other cases (the user doesn't provide EU VAT number or the EU VAT number starts by HU) the amount of VAT would be 27%.
How can I do this?