Button that spawns blocks doesn't work. What should I do?

Hello!

I wanted to make a sandbox, where players can spawn different models. I did a code:

local btn = script.Parent
local frame = btn.Parent
local gui = frame.Parent
local txtbx = frame:FindFirstChild("TextBox")
local finish = txtbx.Text
local zero = 0

btn.MouseButton1Click:Connect(function()    -- button listens for clicks
----------------------------------------------------------------------------------
    local Players = game:GetService("Players")                                  
    Players.PlayerAdded:Connect(function(player)
        player.CharacterAdded:Connect(function(character)                       -- Getting humanoid's root part
            local humrootpart = character:WaitForChild("HumanoidRootPart")
            local pos = humrootpart.Position
----------------------------------------------------------------------------------
            local folder = Instance.new('Folder') -- creating new folder
            folder.Name = "Parts"
            folder.Parent = workspace
            if finish > 0 and finish < 100 then
                repeat
                    zero = zero + 1
                    local part = Instance.new('part') -- creating new part
                    part.Transparency = 0
                    part.Anchored = false
                    part.Shape = 'Block'
                    part.Position = pos + Vector3.new(7, 10, 0)
                    part.Parent = folder
                    part.Size = Vector3.new(3, 3, 3)
                    part.BrickColor = BrickColor.Random()
                    wait(1) -- delay between repeats
                    print("blocks count: ", zero)
                until zero == finish
                zero = 0
                print("zero is 0")
            else -- if value isn't between 1 and 100
                txtbx.Text = "Please enter values between 1 and 100 only"
            end
        end)
    end)
end)

So when player clicks on button, it creates a folder and the number of blocks that the player entered will spawn. But some reason, it doesn't work at all. I don't understand why. I placed almost the same script to a part, so when player touches the part, script will run. And it worked! But when i tried the same thing with gui, it doesn't run. Help!