IF_WORKFLOW does not exist ?

Hello,

i creaed an abap class using the class builder and i want to use this class in a workflow, once i added the class and its method to the workflow, and i did checking, the system said" IF_WORKFLOW does not exist.

i know i can create workflow with objects from the class builder but what is this interface and how to implement it. and do i implement in from within the object definition in the class builder ?

Any suggestions on this matter.

points are awarded

Regards