function abrir(endereco,campos,nome)
{
   campos++;
   y = campos*40-45;
   x = 450;
   tx = (screen.width - x)/2;
   ty = (screen.height - y)/2;
   f = 'width='+x+',height='+y+',top='+ty+',left='+tx+',toolbar=no,location=no,status=no,resizable=no,scrollbars=auto';
   window.open(endereco,nome,f);
}