function isChecked(obj)
{
  return (obj.checked == true)?true:false;
}

function uncheckAll(obj,checkboxes)
{
  for(var i=0; i<obj.elements.length; i++)
  {
    if(obj.elements[i].type == "checkbox" && obj.elements[i].name == checkboxes)
    {
      obj.elements[i].checked = false;
    }
  }
}

function checkAll(obj,checkboxes)
{
  for(var i=0; i<obj.elements.length; i++)
  {
    if(obj.elements[i].type == "checkbox" && obj.elements[i].name == checkboxes)
    {
      obj.elements[i].checked = true;
    }
  }
}

function AllBoxes(name, checkboxes)
{
  var obj = eval("document.forms['" + name + "']");
  var checked = 0;
  var unchecked = 0;
  var checkboxCnt = 0;
  var cnt = obj.elements.length;

  for(var i=0; i<cnt; i++)
  {
    if(obj.elements[i].type == "checkbox" && obj.elements[i].name == checkboxes)
    {
      checkboxCnt++;
      if(isChecked(obj.elements[i]))
      {
        checked++;
      }
    }
  }

// jeigu pazymeti visi - darome uncheckAll()
  if (checked > 0 && checked == checkboxCnt)
    uncheckAll(obj,checkboxes);  
// jeigu nors vienas pazymetas - darome checkAll()
  if (checked > 0 && checked < checkboxCnt)
    checkAll(obj,checkboxes);
// jeigu nieko nepazymeta - darome checkAll()
  if (checked == 0)
    checkAll(obj,checkboxes);  
}