Woocommerce checkout conditional fields

Hello,
So i've got an eshop and i'm trying to add few new conditional fields.
1) There will be a dropdown which will have 2 options. (Receipt or Invoice).
2) When some1 chooses receipt (which will be a default value) he will be able to continue with his order w/o filling any other fields.
3) If some1 chooses invoice he will have to fill 4 new REQUIRED fields to continue. (TAX, Vat, Company Name, Profesion).

I've tried a plugin by woothemes but it doesn't give you the option to add the conditional functionality.

I hope you'll be able to help me out.
Thanks in advance.

Regards,
Edgar.