How do I make players able to change a script in-game via an TextBox?

I want to make players able to change a script in-game via an GUI (TextBox). When they write an number (an ID of a product) in the GUI and press enter, I want to make that the “ID OF THE PRODUCT” get replaced with the number the player writes in the GUI.

THE SCRIPT:
local assetid = “ID OF THE PRODUCT”

local cd = script.Parent.ClickDetector

cd.MouseClick:connect(function(player)

game:GetService(“MarketplaceService”):PromptPurchase(player,assetid)

end)

Please help…