If you already have the outline applied, you can protect the worksheet in code
(auto_open/workbook_open??).

Option Explicit
Sub auto_open()
With Worksheets("sheet1")
.Protect Password:="hi", userinterfaceonly:=True
.EnableOutlining = True
End With
End Sub

It needs to be reset each time you open the workbook. (excel doesn't remember
it after closing the workbook.)

If you're new to macros, you may want to read David McRitchie's intro at:
http://www.mvps.org/dmcritchie/excel/getstarted.htm

Bob Laithwaite wrote:

As soon as I protect a worksheet/workbook the +/- grouping controls I've
created are protected.
How do I protect most of the sheet, but allow these expand/contract grouping
controls to operate normally?

--

Dave Peterson