Hi Ulfah,
I have just did a quick test and the property works perfectly.
oICL.ItemCode = "11KG";
oICL.CountedQuantity = 4;
oICL.WarehouseCode = "01";
oICL.Counted = BoYesNoEnum.tYES;
oICL.UserFields.Item("U_TWM_TEST").Value = "X";
If you have just added your UDFs, please shut down your SBO client and restart it first.
Regards
Edy