You can choose to watch a location for any changes made to the directory on the file system. The Voyager index will be updated immediately if a file in the 'watched' location changes.

note
Watching a location will only work on files that have a 1 to 1 mapping to files on the system. For example, it works well for file-based Rasters, Shapefiles, Office documents, MXDs, Layer Files, etc., but will not currently work for SDE, VPF, or anything else that has a different internal structure than what is displayed as a file on disk.