How to make text move across screen?

How can I make this repeat the message after it is off the screen?

right = false

left = true

speed = 10000

while true do
	wait()
	if right then
		for i=1, speed do
			script.Parent.Position = UDim2.new(i / speed,0,0.5,0)
			wait()
		end
	end
	if left then
		for i=1, speed  do
			script.Parent.Position = UDim2.new((speed - i) / speed,0,0.5,0)
			wait()
		end
	end
end