Rules for Non-employee source?

Hi, I should implement some login for users created with NE source, acting as authoritative source, with the goal of calculate with java code some fields after new user is saved. I already exhausted transforms for doing that. I am seeing in doc that rules aplies to some fixed connenctors (JDBC, AD, WS, etc), do I have some way to put logic into the NE source using rules? Is there some alternative?