How to include multiple membes in an expression?

Hello, I'm wondering how can I include multiple members from a dimension in a Calculated Measure Expression?

Good (single member) ([ActionGroup].[ActionTag].&[147300], [Measures].[Unique Visitors])

#Value Error (multiple members)

([ActionGroup].[ActionTag].&[147300].&[107139], [Measures].[Unique Visitors])

({[ActionGroup].[ActionTag].&[147300], [ActionGroup].[ActionTag].&[107139]}, [Measures].[Unique Visitors])

Any pointer is appreciated

-Lawrence

Is this what you are looking for ?

Aggregate({[ActionGroup].[ActionTag].&[147300], [ActionGroup].[ActionTag].&[107139]} , [Measures].[Unique Visitors])