Detect in VBA if document has been changed

[nsv]

A Word document functions as a kind of engineering drawing that has to be updated from time to time.
To keep a track on these updates a parallel document serves as a log where the changes are described, and to make sure it is filled in every time changes are made, I have an AutoClose macro in the drawing document automatically open the log document.



I should like to make it so, that the log is opened only if changes have been made to the drawing document, but I do not know how to detect that in VBA.
Anyone has a clue?

NSV