SSAS - Scoping on restricted members

Due to a miscommunication in the requirements gathering process I recently had to apply a temporary fix to overwrite values in my cube like so:

SCOPE([MEASURES].[Revenue KPI]);

  SCOPE([Product].[Product].&[11700]);

    THIS = [Measures].[P and L];

  END SCOPE;

END SCOPE;

In this particular cube we have security roles set up that restrict on the [Product].[Product] hierarchy. Users that are members of roles that restrict them from seeing [Product].[Product].&[11700] were complaining about error messages like the one displayed below.

The problem is that we're trying to scope on a member that that user is not allowed to query. So how do we get around that? I pinged a message to Chris Webb and he replied that he had already blogged about this.

http://cwebbbi.spaces.live.com/blog/cns!7B84B0F2C239489A!1563.entry

The solution is shown here and basically works around the issue by creating a named set that is empty if the user is not allowed to view the member:

CREATE HIDDEN SET [BFSelect] AS

  iif(iserror(strtomember("[Product].[Product].&[11700]")),

  {},

  {[Product].[Product].&[11700]}

  );

SCOPE([MEASURES].[Revenue KPI]);

  SCOPE([BFSelect]);

    THIS = [Measures].[P and L];

  END SCOPE;

END SCOPE;

Problem solved, thanks to Chris.