We have a document library that has files which get reassigned to different users, with the "assigned to" column, and we want someone to get notified automatically when a document is assigned to them - do I need to create a workflow that monitors this in some way and then emails that user, or use a task list? I'm having trouble figuring out how to do this. A document may be uploaded and not have anyone assigned to it, then get assigned to multiple people before it is complete, at which point the assigned to field is set to blank.