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
.EnableAutoFilter = True
End With
End Sub

(I wasn't sure what caused your outlining--data|Group or Data|subtotals).)

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

Rick wrote:

When I use the sheet protection feature of Excel, I can not unprotect the
outlining feature of the spreadsheet. I would like to protect some cells in
the spreadsheet, but not disable the outlining expanding and collapsing
feature. I am not asking to edit the outline. I just want to use the
outlining features as a means to navigate large sheets.

Currently, I have to unprotect the sheet in order to expand or collapse the
outline. Is there a way to view a protected sheet with the outlining
features enables?

--

Dave Peterson