How to Modified or permanently delete Field in the DBGrid with Delphi?

how so that I can remove / modify fields in the DB Grid permanently? I use this code: NB : CDS = ClientDataSet DBG = DBGrid Database I use is *.xml

uses
  Windows, SysUtils, Forms, ExtCtrls, Buttons, DB, DBClient, DBGrids,
  Grids, Controls, StdCtrls, Dialogs, Classes;

type
  TForm1 = class(TForm)
        B2: TSpeedButton;
        B3: TSpeedButton;
        DS: TDataSource;
        CDS: TClientDataSet;
        DBG: TDBGrid;
        SD: TSaveDialog;
        RG: TRadioGroup;
        E1: TEdit;
        E2: TEdit;
        L1: TLabel;
        L2: TLabel;
        B1: TSpeedButton;
        B4: TSpeedButton;
        B5: TSpeedButton;
        OD: TOpenDialog;
    var
        FN, FDragOfs: Integer;
        FDragging: Boolean;

    procedure TForm1.FormShow(Sender: TObject);
    begin
       FN := 1;
       RG.ItemIndex := 0;
    end;

    on Button Create --->

    try
       FN := FN + 1;
       CDS.Active := false;
    with CDS.FieldDefs.AddFieldDef do
    begin
       Name := E1.Text;
    case RG.ItemIndex of
       0 :
    begin
       DataType := ftString;
       Size := StrToInt(E2.Text);
    end;
       1 :
       DataType := ftInteger;
    end;

    end;
       CDS.CreateDataSet;
       E1.Text := 'Field'+IntToStr(FN);
       RG.ItemIndex :=0;
    finally
       CDS.Active := True;
    end;

    on Button Export To File ---->

    if not SD.Execute then
       exit
    else
    begin
       CDS.SaveToFile(SD.filename,dfxml);
       CDS.Active := false;
       CDS.FileName := SD.FileName;

    on Button Delete --->

        CDS.Fields.Remove (DBG.Columns.Items [DBG.SelectedIndex] .Field);
        //DBG.Columns.Delete(DBG.SelectedIndex);
        DBG.Columns.RebuildColumns;

    DB Structur e.g like this : 

        <?xml version="1.0" standalone="yes"?> 
         <DATAPACKET Version="2.0">
        <METADATA>
        <FIELDS>
        <FIELD attrname="Number" fieldtype="i4"/>
        <FIELD attrname="Date" fieldtype="string" WIDTH="20"/>
        <FIELD attrname="Name" fieldtype="string" WIDTH="20"/>
        <FIELD attrname="Phone" fieldtype="string" WIDTH="20"/>
        <FIELD attrname="Address" fieldtype="string" WIDTH="20"/>
        <FIELD attrname="Manager" fieldtype="string" WIDTH="20"/>
        </FIELDS>
        <PARAMS/>
        </METADATA>
        <ROWDATA>
        </ROWDATA>
        </DATAPACKET>

so the question of how way I can remove / replace(rename or modified) with another name field that I do not want when Run-Time, i want to delete this line. example:

<FIELD attrname = "Date" fieldtype = "string" WIDTH = "20" />

after I remove Field does not appear, but when I took my application and re-run the database load sa'at back again as before.

sorry about my English.