I have two eDir trees i am synching....a flat tree and a departmental
tree. I am trying to create a policy/rule that if someone creates a user
in the departmental tree (unique in its own container, but not unique to
the entire group of users) with a CN that already exists in the flat
tree..... an email will be sent to the admin account to notify him that
the user was not created. I have tried to figure out how to write
this..... but I can't get it. This is what I am trying to do:

If I'm creating a NEW user
and if the CN of this user already exists in other tree
Send email
Veto

Should it go in the Matching Rules??? Any suggestions would be appreciated.

Thanks, Jordan