Thanks Paul

Sorry for the late response.

I decided on a slightly different workaround which might be useful to
other people. These are the steps I took:

1) create a front sheet ("Startup") which displays a message "You must
enable macros"
2) write an auto_close() Sub which which calls the Sub
Hideworksheets(). This makes all other sheets except "Startup" have
the property xlVeryHidden

Sub Hideworksheets()
ThisWorkbook.Worksheets("Startup").Visible = True
For Each Sheet In ThisWorkbook.Worksheets()
If Sheet.Name < "Startup" Then Sheet.Visible = xlVeryHidden
Next Sheet
End Sub

3) write an auto_open Sub which calls the Sub Showworksheets(). This
checks the date and if it is still in date then makes all other
worksheets have the property Visible

Sub Showworksheets()
For Each Sheet In ThisWorkbook.Worksheets()
If Sheet.Name < "Startup" Then Sheet.Visible = True
Next Sheet
ThisWorkbook.Worksheets("Startup").Visible = xlVeryHidden
End Sub

Sub auto_open()
Dim mydate As Date
mydate = "10-Nov-2006"
If mydate < today Then
MsgBox ("Project expired on " & mydate & vbCrLf & "Press OK to
exit")
ActiveWorkbook.Close
End If
Call Showworksheets
End Sub

4) Be sure to Lock the sheets and only unlock the cells you want the
user to input to. I would also suggest that you hide the formulae in
all cells.

5) Password protect the Modules.

One other thing...save a version without the date check for yourself
otherwise the whole spreadsheet will be useless after the expiry date.

All the best
Lloyd