Update vendTrans Table while PO invoicing x++

/*Go to PurchFormLetter_Invoice
Add below code to get buffers in afterOperationEnd Method*/

protected void afterOperationEnd()
{
FormletterOutputContract purchFormLetterOutputContract;
ParmId parmId,parmID2;
Purchparmline purchParmLineTable;
PurchParmTable purchParmTable;
purchline purchlineTable;
Amount purchPreviousPrice,purchCurrentPrice;
InventTableModule inventTableModuleTable;
VendInvoiceJour vendInvoiceJournal;
Amount costPrice,profitPercentage,salesPrice,salesCost,salesOverHead;
VendTrans updateVendTrans;

str journalLines;

VendInvoiceTrans vendInvoiceTrans;
VendInvoiceInfoTable vendInvoiceInfoTable;

super();

purchFormLetterOutputContract = this.getOutputContract();

journalLines = purchFormLetterOutputContract.parmJournalLines();
vendInvoiceJournal = purchFormLetterOutputContract.parmJournal() as VendInvoiceJour;

if (purchFormLetterOutputContract.parmNumberOfOrdersPosted() > 0)
{
select vendInvoiceInfoTable where vendInvoiceInfoTable.ParmId==vendInvoiceJournal.ParmId
&& vendInvoiceInfoTable.PurchId==vendInvoiceJournal.PurchId;

select forupdate updateVendTrans where updateVendTrans.Voucher==vendInvoiceJournal.LedgerVoucher
&& updateVendTrans.TransDate == vendInvoiceJournal.InvoiceDate
&& updateVendTrans.AccountNum == vendInvoiceJournal.InvoiceAccount;
if (updateVendTrans.RecId)
{
ttsbegin;
updateVendTrans.Txt=vendInvoiceInfoTable.Description;
updateVendTrans.doUpdate();
ttscommit;
}
}
}