There are two classes that make it relatively easy to track changes to nodes (INode) via indirect references: INodeMonitor and INodeTransformMonitor. These classes are necessary to prevent circular references, and unnecessary propagation of reference messages. Both of these classes can be cast to ReferenceTarget.

The INodeMonitor class will retransmit REFMSG_TARGET_DELETED messages from an INode to your plug-in, while the INodeMonitor will in addition send REFMSG_CHANGE messages when PartID is equal to PART_TM

Creation of a reference to an INodeMonitor is shown below:

Interface* ip = GetCOREInterface();
  ReplaceReference(0, static_cast<ReferenceTarget*>(ip->CreateInstance(REF_TARGET_CLASS_ID, NODEMONITOR_CLASS_ID)));