I need help figuring a complex (for me) reverse discount formula

Can any one please help me with this ... my brain is hurting!

I am trying to create a formula to use in EXCEL for a reverse discount but it isn’t quite as simple as that?

An item costs £1000. I have to include a (say) 10% as a royalty within the selling price.
£1000 + 10% = £1100.
This is wrong as Royalty on selling price of £1100 at 10% = £110 which leaves a £10 shortfall.
The correct selling price is £1111.11 which allows the 10% royalty of £111.11 and the original price of £1000 intact.

I need to create an excel formula with two option boxes, one for the original price, one for the percentage, and crucially an automatic answer box which works out the correct selling price as per my example.

I have worked-up a crude excel with the two baseline boxes, original price and percentage, but my "answer" box is a "try it and see what happens" sort of affair.
It works but is bad practice.
I know there will be a formula, but I just can't get a grip on it.

Appreciate any help

Thanks

JBarryD

Thank you very much.
It is so obvious once you have been shown.
When experiencing "Boggle-factor" as I was, the poor old brain just cried "Enough"

Thank you again

JBarryD