How can we make a conditional named set?

I want to make a named set by filtering another named set if it exists. But
below expression does not work:
iif
(
VBA!ISERROR(Count(StrToSet("[NS_Account]"))),
sum(Except(DESCENDANTS([Account].CurrentMember, , LEAVES))),
sum(Except(DESCENDANTS([Account].CurrentMember, , LEAVES),
StrToSet("[NS_Account]")))
)

neither this one:
Except
(
{[Account].Members},
iif(VBA!ISERROR(Count(StrToSet("[NS_Account]"))), {},
StrToSet("[NS_Account]"))
)

Thanks...

Ipek Guven

Iif() returns values, not sets, so second expression won't work. For the
first expression, are you summing the cube default measure (otherwise
the measure should be explicit)?
In any case, you don't need Except for the true condition:

(
VBA!ISERROR(Count(StrToSet("[NS_Account]"))),
sum(DESCENDANTS([Account].CurrentMember, , LEAVES),
[Measures].[MyMeasure]),
sum(Except(DESCENDANTS([Account].CurrentMember, , LEAVES),
StrToSet("[NS_Account]")), [Measures].[MyMeasure])
)


- Deepak

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