procedure TForm1.Button1Click(Sender: TObject);
var Form: TForm;
    Edit: TEdit;
begin
   Form:=TForm.Create(Application);
   Form.Caption:='Тестовое диалоговое окно';
   Form.Width:=420;
   Form.Height:=135;
   Form.BorderStyle:=bsDialog;
   Form.Position:=poScreenCenter;
   with TLabel.Create(Form) do
   begin
      Parent:=Form;
      Left:=8;
      Top:=8;
      Font.Size:=14;
      Caption:='Введите текст:';
   end;
   Edit:=TEdit.Create(Form);
   Edit.Parent:=Form;
   Edit.Left:=8;
   Edit.Top:=32;
   Edit.Width:=400;
   Edit.Font.Size:=14;
   Edit.Text:='';
   with TButton.Create(Form) do
   begin
      Parent:=Form;
      Left:=175;
      Top:=72;
      Caption:='OK';
      Default:=true;
      ModalResult:=mrOk;
   end;
   Form.ShowModal;
   Label1.Caption:=Edit.Text;
   FreeAndNil(Form);
end;