Hi Karl, thanks for the answer. Yes, that helps. It also shows that we not really can rely on return values ;-) Best regards Norbert -- PREINING Norbert https://www.preining.info arXiv / Cornell University + IFMGA Guide + TU Wien + TeX Live GPG: 0x860CDC13 fp: F7D8 A928 26E3 16A1 9FA0 ACF0 6CAC A448 860C DC13