Conditional Action to change price

Is it possible to use a conditional action to change the price of an item, without it showing on the checkout or invoice.

I'm using the UC_VAT module to charge VAT to customers in EU countries and I want to charge customers outside the EU the full price shown (which is VAT inclusive).

So I want to do a CA that checks if a customer is in the EU at the calculate tax trigger, and if not add 20% to the price, so they're charged what the product cost appears to be.

Thanks
Edward