How do i make so the model will follow once in clicked the GUI?

i am a newbie at scripting but i know how to script.I am making a Tycoon Building game I have a problem where i want to make the model follow my mouse cursor once i clicked the GUI button, and i want it continuously follow the cursor once i click it

local player = game.Players.LocalPlayer
local mouse = player:GetMouse()
local function round (n)
	return math.floor(n + 0.5)
end
	
if game.StarterGui.ScreenGui.BuildModeFrame.BuildSelections.IronWall
	then
		game:GetService("UserInputService").InputChanged:Connect(function(input, gameProcessed)
			game.Workspace.walls.ironwall:SetPrimaryPartCFrame(CFrame.new(round(mouse.Hit.Position.X),round(mouse.Hit.Position.Y),round(mouse.Hit.Position.Z)) + Vector3.new(0,5,0))
	end)
end

some parts of this code isn't necessarily needed to be there. Please help and also if you can make this script more shorter that would help a lot , thank you in advance