How to create an Invoice in delivery screen?

Hi everybody.

I am trying to create an invoice in the delivery screen, but i am getting an error "-5002 Invalid total[OINV.DocTotal]". Can anyone tell me how to solve this ?

here is my code

Dim sNewObjCode As String

Dim i As Integer

' Get last added document number (the order that was added)

oCompany.GetNewObjectCode(sNewObjCode)

' this loop adds the different items to the invoice object

i = 0

Do

oInvoice.Lines.BaseEntry = sNewObjCode

oInvoice.Lines.BaseLine = i

oInvoice.Lines.BaseType = SAPbobsCOM.BoObjectTypes.oOrders

oInvoice.Lines.TaxCode = TableLines.Rows(i).Item(4)

i += 1

If i <> TableLines.Rows.Count Then

oInvoice.Lines.Add()

End If

Loop Until i = TableLines.Rows.Count

' Try to add the invoice object to the database

lRetCode = oInvoice.Add()

If lRetCode <> 0 Then ' If the addition failed

oCompany.GetLastError(lErrCode, sErrMsg)

MsgBox(lErrCode & " " & sErrMsg) ' Display error message

Else

cmdInvoice.Enabled = True

MsgBox("inv Added to DataBase", MsgBoxStyle.Information, "Order Added")

End If

Thanks

Mina