Calc Final Sale Price Including % of Sale?

Hi all,

I think this is more of a math problem than an excel problem, but I am hoping there is a function that could help.

I am trying to workout prices for our website. The price is made up of the item cost, the profit % required and VAT where applicable. This then gives the sell price.

However we are charged 3.9% + 20p for every transaction through paypal.

I would like to include this in the final sale price, but because it is based on the final sale price, its not that easy.

for instance £100 sale price x by 103.9%+20p = £104.1 now if paypal deduct their fee it works like this £104.1 x 3.9% +20p = £4.25 - from our £104.1 = £99.84 not £100.

Any help would be greatly appreciated.

Thanks
Kieren