The simplest and most secure method may be just saving the workbook with a
write-password.
File|SaveAs
xl2002 wording: Tools|General Options|give it a nice password to modify
xl2k and before: Tools|Options|and a nice password here.
Then share the password to modify with your selected group.
Excel isn't really a secure environment. If you resorted to a home grown macro,
then all the users would have to do is to open the workbook with macros
disabled.
And to stop the users from saving as a new name is pretty difficult, too. They
could use windows explorer and copy|paste to a new folder (or new name) and then
you'd be sunk.
But if you want to try, put a nice little text file in the same folder as the
workbook. Call it Notes.txt (looks like it might be useful.) Then have the
auto_open macro look for that file. If it finds it, continue. If not, stop.
And check for the name while you're there. (again, this breaks if the workbook
is opened with macros disabled.)
Option Explicit
Sub auto_open()
Dim myFileName As String
Dim keyFileName As String
myFileName = "book8.xls"
keyFileName = "notes.txt"
If LCase(ThisWorkbook.Name) = LCase(myFileName) _
And Dir(ThisWorkbook.Path & "\" & keyFileName) <> "" Then
'ok continue!
Else
MsgBox "Not the correct file--must close--logging sent to the FBI"
ThisWorkbook.Close savechanges:=False
End If
End Sub
(you could use the workbook_open even under ThisWorkbook, too.)
Don't forget to lock the VBA Project, too. Else you'll have inquisitive types
looking at your code and seeing the password.
Inside the VBE, you can lock the project.
Tools|VBAProject Properties|Protection tab.
Give it a memorable password and lock the project for viewing.
If you're new to macros, you may want to read David McRitchie's intro at:
http://www.mvps.org/dmcritchie/excel/getstarted.htm