Enable Outlining in multiple proected worksheets

I am hoping someone can assist me with this one. I'm using the following VBA code to allow users to open/close groups on protected worksheets, but do not know the syntax to have this affect all worksheet tabs. Using the code below, it works on the Highland tab. I have 3 protected worksheets that I need to allow to do this, called:

Highland
Guildford
Southwood


I have posted this code on "ThisWorkbook object:

Private Sub Workbook_Open()
With Worksheets("Highland")
.Protect Password:="password", Userinterfaceonly:=True
.EnableOutlining = True
End With
End Sub

Thank you! It worked beautifully! Very much appreciated.