Переход при нажатии кнопки

#ifndef Unit1H
#define Unit1H
//---------------------------------------------------------------------------
#include <System.Classes.hpp>
#include <Vcl.Controls.hpp>
#include <Vcl.StdCtrls.hpp>
#include <Vcl.Forms.hpp>
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published:    // IDE-managed Components
    TListBox *ListBox1;
    TButton *Button1;
    TEdit *Edit1;
    void __fastcall FormCreate(TObject *Sender);
    void __fastcall Button1Click(TObject *Sender);
private:    // User declarations
    int CurrentIndex, MaxIndex; //<<== Объявить эти переменные
    void __fastcall MyMethod(); //<<== Объявить этот метод
public:     // User declarations
    __fastcall TForm1(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif

#pragma hdrstop
 
#include "Unit1.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
 
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
    : TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TForm1::FormCreate(TObject *Sender)
{
  MaxIndex = ListBox1->Items->Count - 1;
  CurrentIndex = MaxIndex;
  MyMethod();
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
  if(CurrentIndex == 0) CurrentIndex = MaxIndex;
  else CurrentIndex--;
  MyMethod();
}
//---------------------------------------------------------------------------
void __fastcall TForm1::MyMethod() //<<== Эту реализацию метода пишем руками
{
  ListBox1->ItemIndex = CurrentIndex;
  Edit1->Text = ListBox1->Items->Strings[CurrentIndex];
}