Enable outlining in a shared/protected workbook

I would like to know how the following code provided in the Excel Help Best Practice Forums , used to enable outlining on a protected sheet, can be applied to a shared workbook.

Private Sub Workbook_Open()

With Sheet1

.Protect Password:="Secret", UserInterfaceOnly:=True

.EnableOutlining = True

End With

End Sub

After enabling 'Share Workbook' and re-opening the file it presents the following error:

Run-time error '1004':
Method 'Protect' of object '_Worksheet' failed

Can it be modified to allow the outlining of protected sheets when the workbook is shared and the sheet is protected?