Yes, I found the WBS but now it is not updating the WBS status. I am calling Z FM in Update task as I need to call this FM after sales order save event.
Inside Z FM I am calling below functional modules for updating the WBS status.
BAPI_PS_INITIALIZATION
BAPI_BUS2054_GET_STATUS
BAPI_BUS2054_SET_STATUS
BAPI_PS_PRECOMMIT
Not sure What I am missing in it. is there any other way to update the WBS status.( any other FM )