Rule to evaluate if a value exists in a table

I have a operations that is writing 6 values to a table 

Class BHS.Custom.MosaiqCloudPatientsTable Extends (%Persistent, Ens.Request) [ Inheritance = right ]

I need to create a routing rule to evaluate a field in an hl7 ORU message ,  see if it exists in the account column of the table. If it does then allow the message to pass.

This table is not a lookup table. How can I get a function to evaluate a field to this  table?