Cannot use restricted essbase functions: "@ATTRIBUTESVAL"

We are trying to setup a custom piece of code in the FCCS_20 business rule, however we are receiving the following error:

Cannot use restricted essbase functions: "@ATTRIBUTESVAL"

Is there a way around this? We need to reference entity members based on the attributes they've been tagged with. The calc works when we run it in a custom script, but we want to fold it into the consolidation process for obvious reasons.

Has anyone worked with this before and have any advice? Thanks!