Peter,
Here are links about events.
http://word.mvps.org/faqs/macrosvba/InterceptSavePrint.htm
http://word.mvps.org/faqs/macrosvba/DocumentEvents.htm
http://word.mvps.org/faqs/macrosvba/AppClassEvents.htm
http://word.mvps.org/FAQs/MacrosVBA/PseudoAutoMacros.htm
http://msdn2.microsoft.com/en-us/library/aa140934(office.10).aspx

Specifically, the Save button, Ctl-S and File > Save fires the Word Sub
FileSave command.

Sub FileSave()
MsgBox "Trying to save.  Not going to"
End Sub

in a document would override the command (for THAT document).  Only the
messagebox would display.  The file would NOT be saved.

Sub FileSave()
  ActiveDocument.SaveAs Filename:="c:\yadda\NewFile.doc"
End Sub

would make the Save command do a SaveAs with the named filename.

Sub FileSave()
   ActiveDocument.Close wdDoNotSaveChanges
End Sub

would make the Save command close the document, without saving any changes.