Hi i am a new user of drupal. I have being struggling for days to make the billing fields change whenever i select a choice from a checkbox. I live in greece, and i have to put a choice, for the customer if he wants a receipt or an invoice. If he wants an invoice the form must change, so that it has some more fields like VAT number and the name of his company.

To be more clear i want to do something like payment options, if you select credit card payment drupal puts with ajax, fields that are relevant to credit card payments.

Please help me thank you in advance.