Moving Bricks with Mouse but unable to set a range limit?

So today I coded a LocalScript which makes certain bricks with certain names movable when you are holding your left mouse button on them:

local plr = game.Players.LocalPlayer
repeat wait() until plr and plr.Character
local mouse = plr:GetMouse()
local mtarget
local down

mouse.Button1Down:connect(function()
 if mouse.Target ~= nil and mouse.Target.Locked == false and mouse.Target.Name == "BuildingBrick" or mouse.Target.Name == "BuildingShelf" then
  print(mouse.Target.Name)
  mtarget = mouse.Target
  down = true
  mouse.TargetFilter = mtarget or mouse.Target
  end
end)



mouse.Move:Connect(function()
 if down == true and mtarget ~= nil then
  mtarget.Position = Vector3.new(mouse.Hit.X, mouse.Hit.Y, mouse.Hit.Z)
 end
end)


mouse.Button1Up:connect(function()
 down = false
 mouse.TargetFilter = nil
 mtarget = nil
end)

All of this works, but I have been trying to set a range so the brick I'm moving doesn't move too far away from me, I tried a lot of things but I can't manage to work it out, help?