Add attribute to an olap universe

Hi

I am working with an Microsoft OLAP cube and I am finding difficult to find any information.

I have an analysis dimension for Periods like the one below. On the level Period it has the members P01, ...P12.

I am trying to add an attribute to the members whose value is the number of the month.

The reason why I want to do this is because I have two OLAP universes I need to combine. One P1 represents July and in the second universe P1 is January. I was trying to add the attribute in both so I can then merge both universes in a report. What I would need is for P1 being July add an attribute which value is 7, and for P1 being January add an attribute which value is 1. Then I was thinking in merging in the report the dimension Periods using that attribute.

When I try to add an attribute I put a formula like

LEFT([Periods].[Months].[Period].[CurrentMember].[Name],2)

But it does not work.

Any help?

thanks

Teresa