Change Price (Show Without Vat) With Modifiers

hi to all

i am trying to display the product price in the product main page in the following format

100 (80 + VAT)

i can do this by changing the products template and using the $product.price with no problem.

when the product has option modifiers the problems begin

is there a way to get the selected option modifier , add it to the product price and then do the maths?

is there an easier way of doing this?