Using Group-Ungroup in a protected Excel sheet

Mick_Kitcher 

You have to create the grouping/outline while the worksheet is unprotected.

You have to protect the sheet in a special way when the workbook is opened.

Activate the Visual Basic Editor (Option+F11).

Double-click ThisWorkbook under Microsoft Excel Objects in the Project Explorer pane on the left.

Copy this code into the ThisWorkbook module:

Private Sub Workbook_Open()
    With Me.Worksheets("Sheet1")
       .Protect Password:="Secret", UserInterfaceOnly:=True
       .EnableOutlining = True
    End With
End Sub

Replace Sheet1 with the name of the relevant sheet, and replace Secret with the password that you used to protect the sheet (use "" if you didn't specify a password).

Save the workbook as a macro-enabled workbook (*.xlsm).

Make sure that you allow macros when you open the workbook.