PO acknowledgement

Hi, I am trying post PO acknowledgement into sap using ORDERS01.ORDRSP, standard function module

I have only three fields 1.PO number 2.quantity 3. delivery date. when I try to do, iam getting errors like material is different, units are different and quantities are different it PO quantity in acknowledgement is different, my question is how to post with out validations ?

Thanks

Raj