Calling App Package Class Methods by Reference

In the Peoplesoft Approval Workflow Engine the user enters the name of a Application Package and the name of an Application Class belonging to that package for the Workflow engine to call durng processing. This implies that there must be some technique of turning those field names into a callable reference.  I can think of some interesting applications for the technique, but can find no hint how it is done. Any ideas? Is there something like a Dispatch("ApplicationPackage.class.Method") hiding somewhere?

Thanks

PHS