Magento - Optional VAT discount (exemption) for certain products

We have a 1.3.3.0 installation of Magento that requires a feature as follows.

- Each product has a yes/no attribute which can be set for VAT exemption.
- On the cart page we need a box (similar to how the discount coupon works) that will have a check box (or a button), it will state that if the customer qualifies for VAT exemption to click.
- That will then create a discount line that will take off the VAT for each item in the cart that has the VAT exemption attribute set to yes.