Modular Forcefield System Quarry without Redpower

--Modular Forcefield System Quarry without Redpower--
-->Redpower version -> http://www.youtube.com/watch?v=Yrjo253-m6A
-->Computercraft version -> http://postimg.org/image/c20l21d37/

local exitTime = 27 -- change to whatever you want
local timer = os.startTimer(exitTime) -- starts the timer
local cp = 0
local cm = 0
while true do
  local evt, arg = os.pullEvent() -- wait for an event

    if evt == "timer" then
            if arg == timer then -- check if it's the correct timer
                redstone.setOutput("top",true)
            cp = cp +0.5
                print ("Next move!")
        end
    elseif evt == "redstone" then
            timer = os.startTimer(exitTime) -- restarts the timer
            redstone.setOutput("top",false)
        cm = cm +0.5
        print (cm.."x Send items! ")
    end
  if cm >= 250 then --Lava protect
        redstone.setOutput("top",true)
        print ("Send redstonsignal! "..cp)
  end
end