Enhancement in IDOC_INPUT_ORDERS not saving changes after order creation

Question

I have an enhancement at the beginning of the IDOC_INPUT_ORDERS function module used to create sales orders via EDI.  In the enhancement, I take the data records and make some changes to some quantities and units of measure.  After making these changes, I let the function module continue on as normal.  The order does get created with my changes in them, however, the IDoc doesn't reflect my changes.
Here's an example:  An EDI order comes in with 6 EAs of a material.  In my enhancement, I change it from 6 EAs to 2 3PK.  I then let it go on its way.  The order gets created fine with 2 3PKs, however the IDoc after its a ll done still says 6 EAs. 
The enhancement runs before the FM puts the data into the tables it uses. I tried using the last user exit to open the IDoc and editing it there using the EDI_DOCUMENT_OPEN_FOR_EDIT FM but it says its open. 
Can anyone give me any clues on how to make my changes stick to the IDoc?
Thanks,
Curtis

Answer 1

Ok, I figured out why it's not saving.  Not realizing it, but the tables are passed into the FM by reference, so what I'm changing is only a copy.  So what I tried to do is use the 004 (I've also tried the 005) user exits to try to update the actual DB.  I used the following FMs (EDI_DOCUMENT_OPEN_FOR_EDIT, EDI_CHANGE_DATA_SEGMENTS, and EDI_DOCUMENT_CLOSE_EDIT).  The problem is that I can't change them because the IDoc is still open.
Does anyone have any ideas on how I can achieve my goal of changing the IDoc?
Thanks,
Curtis