How to get Order costs with C#

Hello,

I am having huge problems with acquiring order cost data to my program in C#.

I run the "BAPI_PRODORD_COSTING" remote function module. I get an answer that Costing was executed. I also get all suborders from selected order, their texts and numbers.

IRfcFunction orderCosting = rfcRepo.CreateFunction("BAPI_PRODORD_COSTING");

IRfcTable orders = orderCosting.GetTable("ORDERS");

orders.Append();

codePO = codePO.PadLeft(12, '0'); //trailing zeros

orders.SetValue("ORDER_NUMBER", codePO);

orderCosting.Invoke(rfcDestination);

But regardless how much I try I can't get the actual costs.
I tried to get App log with "/SDF/GET_APP_LOG" and a log handle passed from previous function.

All I get is only some unclear data messages which does not correspond to actual cost data I'd expect.

Please help.

Thank you