Hi Joseph,
I think you should create a new Rule for Approver determination.
SPRO->SAP Supplier Relationship Management->SRM Server->Cross-Application Basic Settings->Business Workflow->Process-Controlled Workflow->Business Process Configuration->Define Filter Values for BAdI 'Define Agents'
And assign it to your step in schema. (TA /SAPSRM/WF_PROCESS)
Then you should create a BADI Implementation with defined filter value.
SPRO->SAP Supplier Relationship Management->SRM Server->Business Add-Ins->Business Workflow->Process-Controlled Workflow->Define Agents
As a reference you can use Implementation /SAPSRM/BD_WF_SC_RR_EMPLOYEE.
Important are methods
/SAPSRM/IF_EX_WF_RESP_RESOLVER~GET_AREA_TO_ITEM_MAP
/SAPSRM/IF_EX_WF_RESP_RESOLVER~GET_APPROVERS_BY_AREA_GUID
First creates a mapping for grouping positions.
You can copy it from the class /SAPSRM/CL_IM_WF_RR_EMPLO and just change line
* Verify employee ID of configuration table lv_employee_id = is_current_process_level-resolver_param.
with the requester determination.
Second method you can just copy from /SAPSRM/CL_IM_WF_RR_EMPLO
Best Regards
Konstantin