function ValidaData(DATA, len, type, message )
{
  if( (len != 6) && (len != 8) )
  {
    if( message == null )
    {
      alert("Data inválida"); 
      DATA.focus();
      DATA.select();
    }	
    return false;
  }

  if( type == 2 )
  { 
    // 15/01/1999
    var wDIA = DATA.value.substring(0,2); 
    var wMES = DATA.value.substring(3,5);
    var wANO = DATA.value.substring(6,len+2);
    var wDATA = wANO+wMES+wDIA;
  }
  else
  {
    // 15011999
    var wDIA = DATA.value.substring(0,2); 
    var wMES = DATA.value.substring(2,4);
    var wANO = DATA.value.substring(4,len);
    var wDATA = wANO+wMES+wDIA;
  }
  if( (wDIA == "") && (wMES == "") && (wANO == "") )
    return true;

  if( isNaN(wDATA) )
  {
    if( message == null )
    {
      alert("Data inválida"); 
      DATA.focus();
      DATA.select();
    } 
    return false;
  }
		
  if( wDATA.length != len )
  {
    if( message == null )
    {
      alert("Data inválida"); 
      DATA.focus();
      DATA.select();
    }
    return false;
  }

  bissexto = ( Math.ceil(wANO/4) == Math.floor(wANO/4) );
		
  valid = true;
  if( (wDIA < 1) || (wDIA > 31) )
    valid = false;

  if( (wMES < 1) || (wMES > 12) )
    valid = false;

  if( ( (wMES==4) || (wMES==6) || (wMES==9) || (wMES==11) ) && wDIA>30 )
    valid = false;

  if( wMES==2 )
    if( bissexto ) 
    {
      if( wDIA>29 )
        valid = false;
    }
    else
      if( wDIA>28 )
        valid = false;
					
  if( !valid )
  {
    if( message == null )
    {
      alert("Data inválida");
      DATA.focus();
      DATA.select();
    }
    return false;
  }
  return true;
}