How to calculate percentage markup on selling price?

 In Excel, how can I calculate  Markup percentages on selling prices? Below we have a markup on selling price  calculator.

Like the markup on cost calculator it is based on the  basic formula  of Markups which is is  €Cost + €Markup = €Selling  Price

That is  you add the markup amount to the cost of  the item to get the selling Price but this time the base is the selling price -it is 100% and the relationships are expressed in relation to selling price.