The TechNet documentation on KPI Custom properties has a statement:
"Use a Text property to specify a phrase or a query.
For example, you can type an MDX query that can be used by another report, such as an analytic report, an Excel Services report, or a SQL Server Reporting Services report that uses SQL Server Analysis Services data."
http://technet.microsoft.com/en-us/library/gg185659.aspx
Where can I find an example of this?