Inno Setup - How to create a custom form that allows me to locate the files to decompress?

I am trying to use this code to create a custom form that allows me to locate the files to decompress:

var
  TNewDiskForm :TSetupForm;
  DiskBitmapImage: TBitmapImage;
  SelectDiskLabel,PathLabel: TLabel;
  PathEdit: TEdit;
  BrowseButton: TButton;
  OKButton: TButton;
  CancelButton: TButton;
  Filename: String;
  Path: String;
  Dir: String;
  ModalResult: Longint;


{ Пути поиска файла }
function GetSanitizedPath: String;
begin
  Result := Trim(PathEdit.Text);
end;

procedure CancelButtonClick(CurPageID: Integer; var Cancel, Confirm: Boolean);
begin
  Cancel :=True;
  Confirm :=False;
end;

{ Кнопки Обзор }
procedure BrowseButtonClick(Sender: TObject);
begin
  Dir := GetSanitizedPath;
  if BrowseForFolder(SetupMessage (msgSelectDirectoryLabel), Dir, False) then
    PathEdit.Text := Dir + '\';
  TNewDiskForm.Show;
end;

{ Форма зыкрытия (работает mrOK) }
procedure FormCloseQuery(Sender: TObject; var CanClose: Boolean);
begin
  Path := PathEdit.Text;
  Filename:= ExpandConstant ('data.bin');

  case TNewDiskForm.ModalResult of
    mrOK:
    begin
      if (Path = '') or not FileExists(Path + Filename) then
      begin
        CanClose := false
        MsgBox(FmtMessage(SetupMessage(msgFileNotInDir2), [Filename, Path]), mbError, MB_OK);
      end;
    end;
    mrCancel:
    begin
      CanClose := True;
    end;
  end;
end;

{ запрос диска }
procedure SelectDisk(const DiskNumber: Integer; const Filename, Path: String);
var
  ExitFlag:Boolean;
begin
  repeat
    TNewDiskForm:= CreateCustomForm();
    TNewDiskForm.SetBounds(ScaleX(0), ScaleY(0), ScaleX(377), ScaleY(200));
    TNewDiskForm.CenterInsideControl(WizardForm, False);
    TNewDiskForm.Caption:=SetupMessage(msgChangeDiskTitle);
    TNewDiskForm.Font.Color:= clWindowText
    TNewDiskForm.Font.Height:= -11
    TNewDiskForm.Font.Name:= 'MS Sans Serif'
    TNewDiskForm.Font.Style:= []
    TNewDiskForm.OnCloseQuery:=@FormCloseQuery;

    SelectDiskLabel:=TLabel.Create(TNewDiskForm)
    SelectDiskLabel.SetBounds(ScaleX(72),ScaleY(8), ScaleX(297), ScaleY(72));
    SelectDiskLabel.AutoSize:=False
    SelectDiskLabel.WordWrap:=True
    SelectDiskLabel.Transparent:=True
    SelectDiskLabel.Font.Color:=clBlack
    SelectDiskLabel.Font.Size:=8
    SelectDiskLabel.Caption:=FmtMessage(SetupMessage(msgSelectDiskLabel2), [IntToStr(DiskNumber)]);
    SelectDiskLabel.Parent:=TNewDiskForm
    SelectDiskLabel.ShowAccelChar:= False

    PathEdit:=TEdit.Create(TNewDiskForm)
    PathEdit.SetBounds(ScaleX(8), ScaleY(96), ScaleX(281), ScaleY(21));
    PathEdit.TabOrder:=2
    PathEdit.Text := ExpandConstant('{src}\');
    PathEdit.Parent := TNewDiskForm;

    PathLabel:= TLabel.Create(TNewDiskForm);
    PathLabel.SetBounds(ScaleX(8),ScaleY(80), ScaleX(5), ScaleY(14));
    PathLabel.Font.Color:=clBlack
    PathLabel.FocusControl:= PathEdit
    PathLabel.Caption := SetupMessage(msgPathLabel);
    PathLabel.Parent:=TNewDiskForm

    BrowseButton := TNewButton.Create(TNewDiskForm);
    BrowseButton.SetBounds(ScaleX(296), ScaleY(95), ScaleX(73), ScaleY(23));
    BrowseButton.Parent := TNewDiskForm;
    BrowseButton.OnClick:=@BrowseButtonClick;
    BrowseButton.Caption := SetupMessage(msgButtonBrowse);

    CancelButton := TNewButton.Create(TNewDiskForm);
    CancelButton.SetBounds(ScaleX(296), ScaleY(137), ScaleX(73), ScaleY(23));
    CancelButton.ModalResult := mrCancel;
    CancelButton.Parent := TNewDiskForm;
    CancelButton.Caption := SetupMessage (msgButtonCancel);

    OkButton := TNewButton.Create(TNewDiskForm);
    OkButton.SetBounds(ScaleX(216), ScaleY(137), ScaleX(73), ScaleY(23));
    OkButton.ModalResult := mrOk;
    OkButton.Parent := TNewDiskForm;
    OKButton.Caption := SetupMessage(msgButtonOK);

    TNewDiskForm.ShowModal;

    { закрытие формы (работает mrCancel) }
    case TNewDiskForm.ModalResult of
      mrCancel:
      begin

        TNewDiskForm.Free;
        ExitFlag := ExitSetupMsgBox;

        case ExitFlag of
          True: WizardForm.Close;
          False: SelectDisk (DiskNumber,Filename,Path);
          True: TNewDiskForm.free;
        end;
    end;
  end;
  until ((TNewDiskForm.ModalResult=mrOk) or (TNewDiskForm.ModalResult = mrCancel));
end;

procedure CurStepChanged(CurStep: TSetupStep);
begin
  { Запуск формы распаковки            № диска          место поиска }
  {                                       |                |         }
  if not (FileExists('data.bin')) then  
  if CurStep = ssInstall then  SelectDisk (2, 'Filename','{src}');
end;

This code works ok (it only starts when the file is not present, and if I indicate where it is and the process continues) in older version of Inno Setup (russian version). But I am trying to modify it to work on the last version of Inno Setup (unknown identifier MODALRESULT).

1. How to modify the code to work with the latest version of Inno Setup?

2. How to check more than one file at same time? (filename1, filename2, etc.)