Add an Adhoc Approver when approving the PO requisition

Oracle iProcurement

12.2.5

Is it possible to add an adhoc approver when approving the PO requisition ? 

Business Case is :

1. PO requisition is submitted. 

2. Two approvers bases on AME to generated. The approval priority : 

1st approver : A

2nd approver : B

3. Now approver A would like to add Approver C in the approval loop. Expected new approval priority : 

1st approver : A

2nd approver : C

3rd approver : B

Please help. Thank you ~

Best regards,

May