user Data source with matrix

Hi all ,,

i have a question if you can help me :

i put choose from list in matrix but when i choose item didn't fill in the column and my code is :

** on create form

   oForm.DataSources.UserDataSources.Add("IDS", BoDataType.dt_SHORT_TEXT);

                SAPbouiCOM.Matrix Mat = (SAPbouiCOM.Matrix)oForm.Items.Item("12").Specific;

              //  SAPbouiCOM.EditTextColumn EC = Mat.Columns.It

                Mat.Columns.Item("V_ITM").ChooseFromListUID = "ITM";

                Mat.Columns.Item("V_ITM").ChooseFromListAlias = "ItemCode";

                Mat.Columns.Item("V_ITM").DataBind.SetBound(true, "", "IDS");

***on Item Event

    if ((pVal.ColUID== "V_4"))

                        {

                        //oForm.DataSources.UserDataSources.Item("IDS").ValueEx = val;

                         SAPbouiCOM.Matrix Mat = (SAPbouiCOM.Matrix)oForm.Items.Item("12").Specific;

                  //  SAPbouiCOM.EditTextColumn EC = Mat.Columns.It

                         SAPbouiCOM.EditText c = null ;

                        try

                         {

                             oForm.DataSources.UserDataSources.Item("IDS").ValueEx = val;

                             Mat.LoadFromDataSource();

                         }