Adding new Batch Number to AP Invoice

Question

i am working on adding new batch number to an existing AP IN by SDK function. I try the following codes, no errors prompt but also nothing updated. Can anyone advise me how to add new batch number to AP Invoice? Many Thanks!
Dim ErrMsg As String
Dim ErrCode As Integer
Dim opch As SAPbobsCOM.Documents
opch = oCompany.GetBusinessObject(SAPbobsCOM.BoObjectTypes.oPurchaseInvoices)
opch.GetByKey(5)
opch.Lines.BatchNumbers.Add()
opch.Lines.BatchNumbers.BatchNumber = "3"
opch.Lines.BatchNumbers.Quantity = 3
ret = opch.Update
If ret <> 0 Then
      oCompany.GetLastError(ErrCode, ErrMsg)
      MsgBox(ErrCode & " " & ErrMsg)
End If

Answer 1

Hi ,
Steps to do:
1.Create an User Defined Field on Document Row Level:
Name: Serial / Batch Details
Type: Alphanumeric
Structure: Text
- Create a Formatted Search which will populate the data from Delivery note.
- Put the UDF into the Print Layout of Delivery Order.
Displaying Batch Details
2.   Decide with information is needed from Batch details to be printed out on A/R Invoice
On Bacth Details form (Inventory\Item Management\Batches\Batch Details) we can see all the possible details.
- Batch Number
- Delivered Quantity
- Expiration Date
3.    Build the formatted search SQL command.
By a SQL cursor driven result set we can build a text which contains the list of the delivered batch details separated by new lines. The relations between A/R Invoice and Delivery note is defined on A/R Invoice Form. in columns 45, 46, and 43 
declare @batch as nvarchar(100)
declare @txt nvarchar(max)
set @txt = ''
declare P cursor for SELECT T0.[BatchNum] + space(1)
  + cast(cast(T1.[Quantity] as decimal(19,2)) as nvarchar)
  + space(1) + case when T0.[ExpDate] is null then '' else convert(nvarchar,T0.[ExpDate],102) end
  FROM OIBT T0 INNER JOIN IBT1 T1 ON T0.ItemCode = T1.ItemCode and T0.WhsCode = T1.WhsCode
  and T0.BatchNUm = T1.BatchNum
  WHERE T1.[BaseEntry] =$[$38.45.0] and T1.[BaseLinNum] =$[$38.46.0]
open P
fetch next from P into @batch
while @@fetch_status = 0
begin
set @txt = @txt '\n'@batch +','
fetch next from P into @batch
end
close P
deallocate P
select @txt
4. Defined the formatted search on the A/R Invoice.