Calculated measure based on dimension property

Hi

I have a measure called
[Measures].[Beløb DKK] (that is Amount in danish exchange)

I have a dimension called Finanskonto.
On the dimension is a property

[Finanskonto].[Finanskonto].Currentmember.Properties( "Calc Gruppe")

What i would like is to sum of the amount of all finanskonto where
the
Properties is "IRRE".

But I cant get this to work.
I have tried this
([Measures].[Beløb DKK],[Finanskonto].
[Finanskonto].Currentmember.Properties( "Calc Gruppe")= "IRRE")

but this returns only #VALUE!

Hope anyone could be of help for me.

BR/Thanks

Jan