We had to implement measure which shows values accumulated until the current day in month. All days in the current month are totalized except special days like sundays or holidays. These have a flag ("IsWorkday") in the underlying database, which indicates this.
The values to accumulate are saved on the first day of each month and data is only saved on the first day of each month. (forecast stuff)

In SSAS 2000 we solved this in the following way:
We implemented a calculated measure in the cube, which grabs the values from the start day of the month (OpeningPeriod). Then we used an IIF Function and a MemberProperty called "IsWorkday" to exclude the special days from the calculation by setting the calculated measure to 0 in that case.
it looks like this: Iif([DimTime].CurrentMember.Properties ("IsWorkday")="0",0,[Measures].[testmeasure])

Now we want to rebuild this to SSAS 2005:
In SSAS2005 we don't have Member Properties, but we could use Attributes instead of. Thus an attribute IsWorkday was created in the Time dimension. The calculation which grabs the values from the start day of the month (OpeningPeriod) works.
But how can I exclude the days, for which no data should be calculated?
I tried to combine the Attribute IsWorkday with DimTime.CurrentMember.
like this - (DimTime.CurrentMember,DimTime.IsWorkday,[Measures].[testmeasure])
It works pretty well - but when the first day of the month is marked as "0", all days in the month get no data. This is the case in the year 2006 in which the January starts with a Sunday.

The migration wizard produced some stuff which does not seem to be useful.

Does anyone know a good solution for this problem?