3ds Max dispatches reference messages sent by reference targets to any dependent reference makers by calling ReferenceMaker::NotifyRefChanged(). A reference maker derived class (e.g. a plug-in) will provide a custom implementation of this function. The return result of ReferenceMaker::NotifyRefChanged() is a RefResult enumeration. Most of the time NotifyRefChanged() will return REF_SUCCEED.
Preventing Message Propagation
When a message is received by a reference maker, which it does not wish to be propagated to its observers (ReferenceMakers) then it should return the value REF_STOP. If the message should immediately prevented from being sent to all other ReferenceMakers then the plug-in should return REF_HALT.