To bind receiver dynamically in Workflow, you have to write a Function Module that will provide you manager name of initiator. This FM should be put in public class to be used in Workflow. The provided value will be saved in any table of HR module.
Then you need to call this method from Workflow template. To set binding, you need to pass a value in _WF_INITIATOR.
Using _WF_Initiator Initiator of the workflow (user name).
Here “user name” is a fourteen-character field in the structure US<Name>.
When a workflow is started using an event, this container element does not initially have a value. However, the container element can be assigned a value via the binding from the event container of the triggering event. For this, the binding from the container element _Evt_Creator in the event container to the container element _WF_Initiator in the workflow container must be defined.