var pop_win=null;

function open_win(win_name, file_name, w, h, left, top)
{
  if (pop_win)
  {
    pop_win.close();
  }

  pop_win= window.open(file_name, win_name, 'width='+ w+ ',height='+ h+ ',left='+ left+ ',top='+ top+ ',scrollbars=yes,resizable=yes,status=no,toolbar=no,menubar=no,titlebar=no');
  pop_win.focus();
}