function startCalc(){
  interval = setInterval("calc()",1);
}
function calc(){
  one = document.autoSumForm.firstBox.value;
  two = document.autoSumForm.secondBox.value; 
  three = document.autoSumForm.thirdBox.value;
  four = document.autoSumForm.fourthBox.value;
  document.autoSumForm.fifthBox.value = (one * 1) + (two * 1) + (three * 1) + (four * 1);
}
function stopCalc(){
  clearInterval(interval);
}