In the Data Connection > Manage Sets > Enter the script as new set
=VisualTotals({[Geography].[Geography].[Country].[All], [Geography].[Geography].[Country].&[Germany], [Geography].[Geography].[Country].&[Australia]})
To note: The all members should be always be included as to aggregate just the members included in the set
=VisualTotals({[Geography].[Geography].[Country].[All], [Geography].[Geography].[Country].&[Germany], [Geography].[Geography].[Country].&[Australia]})
To note: The all members should be always be included as to aggregate just the members included in the set