Routing Rule Condition based on RecordMap property

I am currently trying to add a condition to a routing rule that uses the %Source property of a routing rule.  Unfortunately I am getting compile errors when I use the "%", and if I get PROPERTY DOES NOT EXIST if I try and use any of field. I have tried referencing the messages as "Message." , "Record.",  "FullRecordMapClassName." , "Document." . Does anyone know how to reference the properties of a record map in a routing rule, or if it is even possible? Thanks!