How would i detect when a gui tween is done?

So I'm trying to make an animated background for my game menu and i need to detect when the background is done tweening. I tried doing this but it kept erroring:

local Patterntween = script.Parent:TweenPosition(
	
	UDim2.new(0.509, 0,1, 0),
	Enum.EasingDirection.In,
	Enum.EasingStyle.Linear,
	10,
	nil
	
	
)

while true do
	wait()
	if Patterntween.Completed ==  true then
		print("Tween done!")
	end
end

Someone please help!