function click_up(id)
  {
  el=document.getElementById(id);

  if(el.value=='0' || el.value=='') 
   el.value='1';
  else
   el.value++;
  }

 function click_down(id)
  {
  el=document.getElementById(id);

  if(el.value=='1' || el.value=='0' || el.value=='') 
   el.value='0';
  else
   el.value--;
  }