[gJam]

function processTimer(){
           
  if (limit > 0) {
    setTimeout("processTimer()",1000);
    limit--;
  } else {
    timer_hour = '00'
    timer_min = '00'
    timer_sec = '00'
    /*document.testCheck.submit();*/
  }  
  var timer_hour = parseInt(limit/3600);
  var temp_min = limit - timer_hour*3600;
  var timer_min = parseInt(temp_min/60); 
  var timer_sec = temp_min - timer_min*60;
  
  if (timer_hour < 10) timer_hour = '0'+timer_hour;
  if (timer_min < 10) timer_min = '0'+timer_min;
  if (timer_sec < 10) timer_sec = '0'+timer_sec;
  
  // вывод времени
  document.getElementById('hour_timer').innerHTML=timer_hour;
  document.getElementById('minute_timer').innerHTML=timer_min;
  document.getElementById('second_timer').innerHTML=timer_sec;
}

Limit получает значение "снаружи", при генерации страницы..
т.е.
<script type='text/javascript'>Var limit = (предположим) 500;</script>
<script type='text/javascript' src='путь до файла с методом'></script>