Type Coupling to Class Builder Events

[Workflow]

Hello workflowers

Has anyone got an example of an Event Subscription using an ABAP Class Event
as trigger.
See transaction SWETYPV and Object Category "ABAP Class".

I've figured out so far the class must implement the interface IF_WORKFLOW
to be accepted by SWETYPV.
SAP has a few classes implementing this interface see transaction SE24 and
classes CL_SWF*.

Anyone ever done this?

Nate