Looking to add extended warranty price during checkout

Hello

So I and trying to add the ability for the customer to add an extended warranty during checkout. I would like to have them have the choice to select(radio button) the number of years they want the warranty to cover them, up to 4 years. And I would like the rate to be 2% of the total cost of the item being covered per year. 1 year coverage 2%, 2 year coverage 4%, 3 year coverage 6%, etc.

Any help would be great.

Thanks
J.

You can try to use Product Options. By default product options does not support %. You can add some additional fees for the extended warranty...