Querying a Cache Table from a Business Rule

After all these years of doing basic Ensemble work, I am just beginning to venture into using Cache Tables instead of either Data Lookup tables, or what I know of Outside SQL tables using JDBC.  I have several Cache SQL tables that I am building for a project I am working on.  

• I was wondering if it was possible to use a SQL call to look up a value against a Cache SQL table  within a Business Rule? 
• Or is this something that I would have to build a custom function for? 

Within the Business Rule I need to test to see if a Location value exists within this table, and if it does then process sending it through the DTL onto the Business Operation. 

I could use a Data Lookup table to do this, but do not want to duplicate the process if I don't have too.

Thanks

Scott