How to add the multiple values in custom dimensions based on the condition

[Yatiraj Sharma]

Currently I am having a custom dimension defined like this...

Now I want to check if current members has multiple values then I want to add them too. 

e.g. PI7, PI8 then I wan to add them too 

Like [Label].[PI8L] = [Label].[PI7] + [Label].[PI8] + [Label].[PI8_TEST]