STOP update of PO details in Oracle Purchasing when DROP SHIP type sales order line is UPDATED

Based upon our business requirements, we need to STOP all updates to POs in Oracle Purchasing when a DROP SHIP type sales order line is UPDATED in oracle R12. We analyzed the code/standard APIs available/used when sales order lines are updated from oracle sales order form. In our analysis, we found that a standard API 'PO_OM_INTEGRATION_GRP.Update_Req_PO' is called at some point to update the PO details synchronizing with sales order line changes (standard functionality) during the update process.

Have anyone came across such a requirement? We want to avoid changing the standard APIs at all cost but this requirement is critical to our business process.