Replica event - how catch "before" context?

Hi,

in EM_NSFONOTEOPEN (em_before) I do checking if note has item X, if hasnt, I’m adding one.

How can I catch that some note is taken to replicate by replicator, I dont see any EM to do it. My goal is, to add X item before it is replicated. What Extension Manager can I use?

Thanks,

Konrad