How to import a XML file

What do I wrong in importing a XML-file.
unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, xmldom, XMLIntf, msxmldom, XMLDoc, StdCtrls;

type
  TForm1 = class(TForm)
    Memo1: TMemo;
    Button1: TButton;
    XMLDocument1: TXMLDocument;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
  xmlRoot: IXMLNode;
  xmlOpdracht, xmlTarieven, xmlTariefkop: IXMLNode;
begin
  XMLDocument1.FileName := 'TEST.XML';
  XMLDocument1.Active := True;
  try
    xmlRoot := XMLDocument1.DocumentElement;
    xmlOpdracht := xmlRoot.ChildNodes.FindNode('Opdracht');
    xmlTarieven := xmlOpdracht.ChildNodes.FindNode('Tarieven');
    xmlTariefkop := xmlTarieven.ChildNodes.FindNode('Tariefkop');

    while Assigned(xmlOpdracht) do
    begin
      xmlTarieven := xmlOpdracht.ChildNodes[0];

      while Assigned(xmlTarieven) do
      begin
        xmlTariefkop := xmlTarieven.ChildNodes[0];

        while Assigned(xmlTariefkop) do
        begin
          if xmlTariefkop.NodeName = 'Factuurnetto' then Memo1.Lines.Add(xmlTariefkop.Text);
          //....
          xmlTariefkop := xmlTariefkop.NextSibling;
        end; //xmlTariefkop

        xmlTarieven := xmlTarieven.NextSibling;
      end; //xmlTarieven

      xmlOpdracht := xmlOpdracht.NextSibling;
    end; //xmlOpdracht

  finally
    XMLDocument1.Active := false;
  end;


end;

end.
included the xml-file

greetings,
Henk van den Boogaard
TEST.XML