Incremental indexing

Is it possible for DevonThink to incrementally index documents? I have a folder where I keep some documents and I don’t want them copied into DT database. I have indexed the documents in that folder. However, what I can’t figure out is what happens when I add new documents into that folder. I would hate to re-index the folder from scratch everytime and I wonder if there is something like a “watch this folder” facility such that DT can watch additions to the folder and index them automatically.