setting the VendReceiptsListTrans.InventQty from x++

I have created a batch job to process a receipts list. 
My code creates the receipts list however i cannot seem to get the VendReceiptsListTrans.InventQty to update, the value is always nothing.

Is there a different way to do this?



private void postReceiptList(PurchTableContract purchTableContract)
{
   PurchFormLetter                       purchFormLetter;
   PurchFormLetter_ReceiptsList_Extended purchFormLetter_ReceiptsList_Extended;
 
   PurchId 				 purchId;
   PurchTable 			         purchTable;
   PurchLine                             purchLine;
   ItemId                                itemId;
   LineNumber                            lineNumber;
   PurchQty 				 purchQty;
   container                             lineNumberCon;
   Counter                               ctrJournalLines;
   int 				         i;
   str                                   responseMessage;
   Query                                 query;
   SysQueryRun                           chooseLinesQuery;
   ListEnumerator                        leReceiptListLines = new ListEnumerator();
   PurchLineContract                     purchLineContract;


        purchId = purchTableContract.PurchId();

        purchTable = purchTable::find(purchId);
        if (!purchTable)
        {
            throw error(strFmt("Purchase order '%1' not found.", purchId));
        }

        leReceiptListLines = purchTableContract.journalLines().getEnumerator();
        leReceiptListLines.reset();

        while (leReceiptListLines.moveNext())
        {
            ctrJournalLines++;
            purchLineContract = leReceiptListLines.current();

            itemId =      purchLineContract.ItemId();
            lineNumber =  purchLineContract.LineNum();
            purchQty =    purchLineContract.PurchQty();

            if (!itemId)
            {
                throw error("ItemId cannot be empty.");
            }

            if (!lineNumber)
            {
                throw error("lineNumber cannot be empty.");
            }

            if(purchQty == 0)
            {
                throw error(strFmt("Qty cannot be zero for item %1, 
                            linenum %2", itemId, lineNumber));
            }

            select forUpdate purchLine
                   where purchLine.PurchId == purchId
                         && purchLine.ItemId == itemId
                         && purchLine.LineNumber == lineNumber;

        if (purchLine)
        {
             purchLine.PurchReceivedNow = purchQty;
 
             purchLine.update();
        }
        else
        {
            throw error(strFmt("PurchLine not found for purchase order %1, 
                               ItemId %2, lineNumber %3", purchId, itemId, lineNumber));
        }

                  

        query = new Query(queryStr(PurchUpdate));

        query.dataSourceTable(tableNum(PurchTable)).addRange(fieldNum(PurchTable,PurchId)).value(queryValue(purchId));
        
        query.dataSourceTable(tableNum(PurchLine)).addRange(fieldNum(PurchLine,lineNumber)).value(queryValue(lineNumber));

        chooseLinesQuery = new SysQueryRun(query);
    }

    ttsBegin;


  purchFormLetter = purchFormLetter_ReceiptsList_Extended::newReceiptsListFromChooseLineQuery(chooseLinesQuery,purchTable);

        PurchFormLetter.parmLineList();

        purchFormLetter.update(purchTable,
                            purchId,
                            systemDateGet(),
                            PurchUpdate::ReceiveNow,
                            AccountOrder::None,
                            false,
                            false);

    ttsCommit;
}