you add code Close event of the Document (on VBA->ThisDocument, past this code):
Private Sub Document_Close()
Dim strFile As String
'
' Change strFile to the Path and document name.
' the Extension should be (.docm, macro-enabled document)
'
' on this demo, i am saving it as "new.docm" on user's Document folder
'
strFile = Environ$("userprofile") & "\documents\new.docm"
' save it
Me.SaveAs2 saveToFileName(strFile), wdFormatXMLDocumentMacroEnabled
End Sub
Private Function saveToFileName(ByVal strFile As String) As String
Dim file As String
Dim ext As String
Dim i As Integer, s As String
' get the extension
i = InStrRev(strFile, ".")
If i <> 0 Then
ext = Mid$(strFile, i)
End If
' get only the path+filename (without extension)
file = Replace$(strFile, ext, "")
' new file has date on it
s = file & Format$(Date, "_dd_mm_yyyy") & ext
i = 1
' loop until we get "New" file
Do While Len(Dir$(s)) <> 0
s = file & Format$(Date, "_dd_mm_yyyy") & "(" & i & ")" & ext
i = i + 1
Loop
saveToFileName = s
End Function