type
  TForm1 = class(TForm)
    ListBox1: TListBox;
    btnKundeNeu: TButton;
    procedure btnKundeNeuClick(Sender: TObject);
  private
    { Private declarations }
    FKundenListe: array of TBankKunde;
    procedure UpdateListbox;
  public
    { Public declarations }
  end;

var
  Form1 : TForm1;

const
  FRMCAPTION = 'Meine kleine Bank - %s';

implementation

{$R *.dfm}

procedure TForm1.UpdateListbox;
var
  i : Integer;
  KundenName : string;
  BankKunde : TBankKunde;
begin
  Listbox1.Clear;
  for i := 0 to length(FKundenListe) - 1 do
  begin
    BankKunde := TBankKunde.Create;
    try
      BankKunde := FKundenListe[i];
      KundenName := BankKunde.Name;
    finally
      BankKunde.Free;
    end;
    ListBox1.Items.Add(KundenName);
  end;
end;

procedure TForm1.btnKundeNeuClick(Sender: TObject);
var
  BankKunde : TBankKunde;
  KundenName : string;
  len: Integer;
begin
  KundenName := InputBox('Neuer Kunden', 'Name des Kunden:', '');
  BankKunde := TBankKunde.Create;
  try
    try
      BankKunde.Name := KundenName;

      len := length(FKundenListe);
      SetLength(FKundenListe, len + 1);
      FKundenListe[len] := BankKunde;
    except
      on E: Exception do
        MessageBox(Handle, PChar(E.Message), PChar('Neuen Kunde anlegen'), MB_ICONSTOP);
    end;
  finally
    BankKunde.Free;
  end;
  UpdateListbox;
end;