Do we have webservice for PO Approvals for setting up an auto approval

Do we have webservice for PO Approvals and is it possible to do any customizations for setting up an auto approval at the top level management in PO for example MD is having 2 email id's and user account is available for only 1 email id. Whenever MD approves with other email where user is not available in system, we would like to recognize the same from Database and update the PO approval workflow status as Approved