Adding a Buy X Get Y for % discount

My client wants to have an coupon for his store to allow shoppers to buy three products of a certain category and get a discount for those three products. For example buy three ties for $90, instead of full price. I see that you have a buy x get y free, but we don’t want to give away free, but instead we want to apply a discount. If that’s not possible, then can the cart recognize if there are three items of certain category and apply the discount in the store?
Is this possible to do with Wix code? And if so, where can I find a developer?

I’m pretty sure that you can do it without using code. Please contact Wix Support team regarding this matter as they know best about the Wix Stores feature.