I often work on an email campaign with a coworker at another location. I would like to be notified immediately if I try to open the document while he is already working in it. Microsoft Word has this function - documents are locked after one person opens them, and no one else can get in. The system you have wastes time because we don't find out that both of us are in the document until both of us have already made changes (and some changes get lost).
On another subject, please label the Layout building blocks so people can understand what the differences are between them and how each should be used. They look very similar!