Blocking duplicate batches during GR (101's)

Hi All;

I have a requirement to prevent duplicate batch postings during Goods Receipt (101).

My scenario is:

A GR (101) posting will be performed for material “A” using Batch “B” with quantity 5tons.

Another incorrect movement (duplicate – 101mvt) will be entered with the same combination (material “A” using Batch “B” with quantity 10tons.

I need to block the duplicate 101mvt. However, it must still be possible to reverse (102mvt) the original 101 in case the qty was entered incorrectly.

The unique check should therefore be on Material movement, Material & Batch combination.

Also, if we decide to use a report to reveal duplicates (instead of system block), which tables will be useful? I’ve investigated MCHB, but only the qty is updated (no duplicate record created). The only table I can think of is MSEG (and that’s a lot of data to search…)

Thanks