# Database Discussions > MDX and Analysis Services >  Calculated Measure

## luis.silva

I have a calculated measure with the mdx expression like:

sum(
{
 [Plano Contas Geral].[Parent].&[23.1.2],
 [Plano Contas Geral].[Parent].&[22.1],
 [Plano Contas Geral].[Parent].&[22.2],
 [Plano Contas Geral].[Parent].&[22.8],
 [Plano Contas Geral].[Parent].&[26.9],
 [Plano Contas Geral].[Parent].&[21.9],
 [Plano Contas Geral].[Parent].&[26.1.8]
}, [Measures].[Credito] 
)

But, sometimes there some members in the set specified in the sum function that do not exist, in this case I get an error when 
olap engine parses it. How can I get it to work, even when one of the members doesn't exist?

Help would be appreciated,

Luis Silva

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