Secondary Approval Requirement for Payables Invoices

Business wants to have two level of approvals on an invoice-

1. First approval - Cost Center Manager and moves up in the job level hierarchy based on amount defined within the rule

2. Second Approval - It should be assigned to first level approver's supervisor

We are able to accomplish first level approval with simplified workflow rules spreadsheet (BPM spreadsheet). We are not able to get 'Start Approver' for second level approver and need your help in understanding how to achieve it.

Has anyone faced similar requirement and is there any solution for it?