How do I make my script work while holding the tool?

I am making a sandbox game that locks you in first person and I want to make one of my tools I have allow you to move your cursor when it is equipped. I don't want any of my other items to allow you to move your cursor in first person.

Here is my script:

local Tool = script.Parent

if Tool.Equipped then local plrGui = game.Players.LocalPlayer:WaitForChild("PlayerGui")

local screenGui = Instance.new("ScreenGui", plrGui)

local txtButton = Instance.new("TextButton")
txtButton.BackgroundTransparency = 1
txtButton.Size = UDim2.new(0, 0, 0, 0)

txtButton.Modal = true

txtButton.Parent = screenGui

if Tool.Unequipped then
	txtButton.Modal = false
end

end