How to identify a user-change in USEREXIT_CHECK_VBAP

Question

Hello,
I am writing a bit of code that will overwrite the payment terms in a sales order item based on a number of factors. (ship-to, incoterms, document type, etc)
I am using the following program  MV45AFZB at Exit : USEREXIT_CHECK_VBAP. I am using this exit as the users need to see the payment terms after an item has been entered into the sales order and not have the value determined at sales order save.
I am not using USEREXIT_MOVE_FIELD_TO_VBAP as it is only triggered once at the time of creation and not when I change the document. I need it in USEREXIT_CHECK_VBAP as users could change the incoterms  in VA02, so the code must be redetermined.
My code is working as expected, however, I have a problem when a user enters a sales order item line and then manually changes the payment terms, as my code then is over writes the users values.
The flow is as follows
As user creates a sales order
They populate the sales order header
They populate material number and qty
User exit USEREXIT_CHECK_VBAP is triggered and correctly determines the payment terms
The user then double clicks on the sales order item and decides to overwrite the payment terms.
My user-exit is retriggered and check to see if XVBAP-UPDKZ = I (insert)
As it is still an insert, my code triggers.
I have tried to check YVBAP, but no entry exist as it stills is seen as in insert? What I really need to know that while it is still an insert, the user has change the field value and my code should not over write the users value.

Answer 1

Hi
Please, read carefully SAP Note 178328 - Problems due to incorrect user exits in SD.
It says:
In general, the following connection exists between the update indicator
and the Y tables:
   o When you create a document, only the update indicator 'I' can exist
   in the X tables (or sometimes the update indicator remains
   initial). No records exist in the Y tables.
  o When you change a document, the following cases may occur:
     - You add a table entry. There is only one entry in the X table
     that has the update indicator I. There is no entry in the Y
     table.
and it goes on with useful information.
I hope this helps you
Regards
Eduardo
Edited by: E_Hinojosa on Feb 20, 2012 9:20 AM