It depends on what way you’d wanna use the pay the robux (Dev Products, Gamepasses, etc)
This service handles all of the purchases & in-game transactions that players buy with robux, you can look at the functions/events that have PromptPurchase in them
After you make your purchase, you can implement a check if they have purchased the item or not & if they have, you can add your GUI’s note to whatever you want to enter using a TextBox I presume
local MarketService = game:GetService("MarketPlaceService")
local ProductID = 00000
MarketService.PromptPurchaseFinished:Connect(function(Player, ProductID, PurchaseCheck)
if PurchaseCheck == true then
--Create your note system here
end
end)
We can tell you how to do it, however we aren’t supposed to spoon-feed you our code. Are you familiar whatsoever with scripting? If not, I’d suggest you hire a scripter, or commission one.