Create new sales line and packing slip line after opening PackingSlip form (salesEditLines)

Hi,

I have requirement like..

After opening packing slip form (Sales Order/ Posting/ Packing Slip)the prompt will ask the new item and quantity. Once user enter the item and quantity, the new line need  be added in sales line and the same into Packing Slip line. 

For that , I used SalesLine.createline() to create a sales line. The new lines showing in sales Table form. But that is not reflected into packing slip form(SalesEditLines) . I used salesFormLetter.update() method, this method is creating duplicates record in all the sales parm table(SalesParmLine, SalesParmUpdate, SalesParmTable). 

Any one please help to resolve this. I am using AX 4.