Assigning Multiple agents to TS31000007 using BADI_CATS_APPROVAL~DETERMINE_APPROVER

For CATS approval, we are using BADI_CATS_APPROVAL~DETERMINE_APPROVER to assign agents to standard task TS31000007. Export parameter RV_APPROVER from the BADI method is not a table, so we are not able to allocate multiple 'US' objects directly. We have tried to use a role as an object, objecttype 'AG', but this does not seem to work. Any ideas on how else to add multiple agents to the workitem using the BADI? If role (AG) as an object type is not accepted, which object types (other than user (US) ) are then valid in the BADI? Regards, Karin.