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

Ruth Betts wrote:

I've just created a fairly complex work sheet with some grouped columns. I
wish to protect some cells with formulas but have other people enter data to
the rest - pretty easy stuff. However, I can't find a way to allow other
users to expand and collapse grouped columns (which is necessary for
practical reasons given number of cols and that most will only need to use
one or 2 groups).

Please advise if there is a way round this.

--

Dave Peterson