Correction of posted packing slip through X++

Hi All, 

I wanted to correction of posted packing slip through X++ code. 

Suppose I have 3 lines in salesLine and I have to correct few one of them. I have manage to do following code so far, but i am confuse how i can mark the specific line for correction. 

[canBeCanceled, canBeCorrected] = custPackingSlipJour.canPackingSlipBeCanceledOrCorrected();

if (canBeCorrected)
{
salesFormLetter = SalesFormLetter::construct(DocumentStatus::PackingSlip);
//If the correct VersioningUpdateType is not set the system will try to create a new packingslip
salesFormLetter.parmVersioningUpdateType(VersioningUpdateType::Correction);
// Set the journal want to cancel
salesFormLetter.parmCallerTable(custPackingSlipJour);

//The rows below are very important. Do not know why (from google)
salesFormLetter.allowEmptyTable(true);
salesFormLetter.initAllowEmptyTable(true);
salesFormLetter.multiForm(true);

// Update
salesFormLetter.update(
salesTable,
custPackingSlipJour.DeliveryDate,
SalesUpdate::DeliverNow);
}

Above lines of code are not sufficient for correction of packing slip. 

Anybody have any idea about this??