VAT Exemption - If checkbox on checkout page checked

I have the need to acheive the following:

If a checkbox is checked on the checkout page - The customer gets products with TaxCode ‘2’ as Tax Exempt - But all other products stay Taxable.

The user would also have to enter some text into a ‘new’ field, that would save against the order.

Any ideas as to the ‘best’ way to acheive this?


Also, is it possbile to make the ‘Tax Rate Depends On’ product rather than shipping address?