How do I add a limit for skipping? [closed]

How to add a limit for player skipping stage,like I have 5 stages and they can only skip until stage 5

local MPS = game:GetService("MarketplaceService")
MPS.ProcessReceipt = function(receiptInfo)
local x = game.Players:GetChildren()
local done = false

for i=1,#x do
    if x[i].userId == receiptInfo.PlayerId then
        if receiptInfo.ProductId == 0 then
            if done == false then
                done = true
                x[i].leaderstats.Stage.Value = x[i].leaderstats.Stage.Value + 1
                x[i]:LoadCharacter()
                done = false
            end
        end
    end
end

return Enum.ProductPurchaseDecision.PurchaseGranted 

end