>>Why not to add a bit field IsProcessed (or Processed) to Event table? When you do the work in your robot process you update the flag and therefore you will not select same records again.
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>This table is read only. It is a client site and we cannot alter it. So, we can rely only on the existing data. This is why we face some issues like that.

Do you store somewhere the already processed IDs? Without storing this info, can you explain again how can you filter (your idea) already processed records?