Moving a player until the key is released?

Okay so I have a Localscript found in the player's screengui in startergui. It's basic function is simple. Move a image frame when you press a letter. Here is my problem, when the user holds down a key I want the player to keep moving until they let go of the key, how exactly would I do this?

The code:

repeat wait() until game.Players.LocalPlayer.PlayerGui
----------------------------------------------------------
-- Disable roblox's dumb stuff
---------------------------------------------------------- 
game.StarterGui:SetCoreGuiEnabled("All", false)
----------------------------------------------------------
-- Global Variables
---------------------------------------------------------- 
local Player = game.Players.LocalPlayer
local Mouse = Player:GetMouse()
local sprite = script.Parent.Player
----------------------------------------------------------
-- Movement
----------------------------------------------------------
function moveLeft()
	sprite.Position = sprite.Position - UDim2.new(0.01,0,0,0)
end 
function moveRight()
	sprite.Position = sprite.Position + UDim2.new(0.01,0,0,0)
end 
----------------------------------------------------------
-- Keyboard input
---------------------------------------------------------- 
Mouse.KeyDown:connect(function(Key)
	if Key == "a" then
		moveLeft()
	end
	if Key == "d" then
		moveRight()
	end
end)

I'd use a 'while' loop and some static boolean values to make sure that it's doing what it should be doing at a given time.

isGoingLeft = false
isGoingRight = false

Mouse.KeyDown:connect(function (Key)
	if Key:lower() == "a" then
		isGoingLeft = true
		while isGoingLeft do
			if isGoingLeft == false then
				break
			end
			moveLeft()
			if isGoingLeft == true then
				wait(.25)
			elseif isGoingLeft == false then
				break
			end
		end
	end
	if Key:lower() == "d" then
		isGoingRight = true
		while isGoingRight do
			if isGoingRight == false then
				break
			end
			moveRight()
			if isGoingRight == true then
				wait(.25)
			elseif isGoingRight == false then
				break
			end
		end
	end
end

Mouse.KeyUp:connect(Key)
	if Key:lower() == "a" then
		isGoingLeft = false
	end
	if Key:lower() == "d" then
		isGoingRight = false
	end

Mouse.KeyDown:connect(function(Key)
	if Key== "a" then 
		moveLeft()
	until Key ~= "a"
	end

Try that?