I'm trying to put together an excel formula that will tell me the required gross price before fee's to result in a desired net price (example $100). The items I sell all incur fees for example; 8.5%+$0.30 ebay fee from gross price and 4.5%+$0.20 paypal fee from the same start price.

I also need formulas to calculate the Ebay and Paypal fees aswell.

D18 = Net price ($100)
D19 = Ebay fee
D20 = Paypal fee
D23 = Gross amount

Any expert advice would be much appreciated on what might just be simple calculations.