This sounds like a good way. If I Know the IR I could read EKBE with that DOC#. Its part of the composite key so it might be expensive. I could also create a custom Index for this..... The get PO and reread EKEBE for all "Q" rows for that PO. That should give me all IRs for that PO.
I also like the idea of creating a custom text id and during the creation of a new IR, store the IR being reversed. (This is all done in one batch process now).
As a last resort, I did see a CI Include in DRSEG. I could wrap some code up and utilize the extensionin concept and pass IR data via my wrapper and update the DRSEG structure using the MRM_INVOICE_CREATE / POST.
Thank you all for your help.
Best regards.