Windows 2003 Server DFS issue with open files

Hello, we are running 2003 server R2 with two dfs shares. It seems that when user A user opens a file on the dfs share (an excel file) then user B opens the same file, user B never recieves a notice that he file is open. When we point these two users to the actual shares and not use dfs at all, user B does get the message that the file is open by user A. Is this normal?