Mark,

Do you see anything wrong with this. You have more experience with BeforeSave bugs than I do. I'm thinking that, if it works, it will let the book(s) be viewed and manually edited in 2010 There must be a reason Management wants people to use it.

ThisWorkbook Code:
Private Sub Workbook_BeforeClose(Cancel As Boolean)
  CreateWarningSheet
End Sub
Private Sub Workbook_BeforeSave(ByVal SaveAsUI As Boolean, Cancel As Boolean)
 CreateWarningSheet
End Sub
Private Sub Workbook_Open()
  DeleteWarningSheet
End Sub
Module Code, although it too could go in the workbook's code page.
Sub CreateWarningSheet()

If WarningSheetExists Then Exit Sub
  Application.ScreenUpdating = False
  Sheets.Add After:=Sheets(Sheets.Count)
  Sheets(Sheets.Count).Name = "WarningSheet"
  Application.ScreenUpdating = True
  Sheets("WarningSheet").Activate

End Sub
Sub DeleteWarningSheet()

Application.DisplayAlerts = False
  If WarningSheetExists Then Sheets("WarningSheet").Delete
Application.DisplayAlerts = True

End Sub
Function WarningSheetExists() As Boolean

On Error Resume Next
If Sheets("WarningSheet").Name <> "WarningSheet" Then
  WarningSheetExists = False
Else
  WarningSheetExists = True
End If

End Function