Post packing slip using shipment through x++ in Dynamics AX 2012

Hello,

I am trying to post a single packing slip for multiple sales orders through code using wmsshipment.

If I only use this line of code:

     SalesFormLetter.update(wmsShipment,systemDateGet(), SalesUpdate::DeliverNow, AccountOrder::Account);

Instead of posting packing slip for one specified shipment, it includes lines from all sales orders that are ready to to pack slip posted.

But if I do this:

    Set shipmentsToPostSet = new Set(Types::String);   
    WMSShipment wmsShipment = WMSShipment::find('SHP0000034');

    shipmentsToPostSet.add(wmsShipment.shipmentId);   
    salesFormLetter.parmLineIdSet(shipmentsToPostSet.pack());   
    SalesFormLetter.update(wmsShipment,systemDateGet(), SalesUpdate::DeliverNow, AccountOrder::Account);

It posts packing slips only for sales orders associated with the shipment but creates separate packing slips for each sales order.

I want to get it to consolidate the packing slip.

Can anybody please help with this issue if you have any information?

Thanks,

Charu Jadhav