Multi level requisition approvals

Hi All,

My purchase requisitions are coming through interfaces, here when we have requisition initially in jde amount is zero and after all the process (approvals) when it got converted into PO at the time users will update amount based on quotes.  Our requirement is all requisition has to go multi level of approvals, for example we have requisition order # 1200001/OR for item quantity 10 with amount zero.  First it has to go site supervisor approval, then HOD approval, then stores in-charge approval, then project manager approval and so on..  Can you please some one help how to handle this scenario.