Posting Product receipt for PO

Hi, Below sample code used to post product receipt for specific PO.

purchTable = PurchTable::find(‘PO0012555’);
purchFormLetter = PurchFormLetter::construct(DocumentStatus::PackingSlip);
purchformLetter.getLast();
purchFormLetter.transDate(transDate);
numberSeq  = NumberSeq::newGetNum(PurchParameters::numRefPurchPackingSlipId()).num();
purchFormLetter.update(purchTable,
“14”,// numberSeq, //this is coming out blank
transDate,
PurchUpDate::All,
AccountOrder::None,
false,
false);

• Ax 2012