conditional sentence MDX

Hello,

What's the sintax for a conditional sentence MDX for a Universe with source BW?

I have the following:

<EXPRESSION>IIF(@Select(Indicad. Meta / Real\L01 Indicad. Meta / Real)="REAL",@Select(Ratios\Reclamos Oper. Acu.),0)</EXPRESSION>

In the universe this sentence is correct but in the webi report I have a error:

A database error ocurred. The database error text is: The MDX query WITH MEMBER

[Measueres].[...]

..

failed to execute with the error Unknown error. (WIS 10901)

Thank you.

Hugo.