public function tagdup($nDup = '', $dVenc = '', $vDup = '')
{
$this->zTagcobr();
$dup = $this->dom->createElement("dup");
$this->dom->addChild($dup, "nDup", $nDup, false, "Número da Duplicata");
$this->dom->addChild($dup, "dVenc", $dVenc, false, "Data de vencimento");
$this->dom->addChild($dup, "vDup", $vDup, true, "Valor da duplicata");
$this->dom->appChild($this->cobr, $dup, 'Inclui duplicata na tag cobr');
$this->aDup[] = $dup;
return $dup;
}