Thanks Himavath,
I was just trying to use VBFA to establish one to one relation with Material Document, line item and Delivery line item.
I checked the exit J_1I7_USEREXIT_EXCISE_BEF_SAVE but it accesses only J_1IEXCDTL and J_1IEXCHDR TABLES.
Now I am trying for J_1I7_USEREXIT_DEPOT_BEF_SAVE table, I think it will solve my purpose.
I set the breakpoint and it is triggering at the time of saving the J1IG document.
I will let you know how it works out.
Thanks again Himavat and Shailesh.
Your reply has been very helpful