Отлов нажатия NumLock и управление им

  public class Hook : IDisposable {
    #region Declare WinAPI functions
      [DllImport("kernel32.dll")]
      private static extern IntPtr LoadLibrary(string lpFileName);
 
      [DllImport("user32.dll")]
      private static extern IntPtr SetWindowsHookEx(int idHook, KeyboardHookProc callback, IntPtr hInstance, uint threadId);
      [DllImport("user32.dll")]
      private static extern IntPtr CallNextHookEx(IntPtr idHook, int nCode, int wParam, IntPtr lParam);
      [DllImport("user32.dll")]
      private static extern bool   UnhookWindowsHookEx(IntPtr hInstance);
    #endregion
    #region Constants
    private const int WH_KEYBOARD_LL = 13;
    private const int WH_KEYDOWN     = 0x0100;
    #endregion
 
    // код клавиши на которую ставим хук
    private int _key;
    public event KeyPressEventHandler KeyPressed;
 
    private delegate IntPtr KeyboardHookProc(int code, IntPtr wParam, IntPtr lParam);
    private KeyboardHookProc _proc;
    private IntPtr _hHook = IntPtr.Zero;
 
    public Hook( int keyCode ) {
      _key = keyCode;
      _proc = HookProc;
    }
 
    public void SetHook() {
      var hInstance = LoadLibrary("User32");
      _hHook = SetWindowsHookEx(WH_KEYBOARD_LL, _proc, hInstance, 0);
    }
 
    public void Dispose() {
      UnHook();
    }
 
    public void UnHook() {
      UnhookWindowsHookEx(_hHook);
    }
 
    private IntPtr HookProc(int code, IntPtr wParam, IntPtr lParam) {
      if( (code >= 0 && wParam == (IntPtr)WH_KEYDOWN) && Marshal.ReadInt32(lParam) == _key ) {
 
        // бросаем событие
        if( KeyPressed != null ) {
          KeyPressed( this, new KeyPressEventArgs(Convert.ToChar(code)) );
        }
      }
 
      // пробрасываем хук дальше
      return CallNextHookEx(_hHook, code, (int)wParam, lParam);
    }
  }

public class Form1 : Form {
  private Hook _hook;
 
  public Form1() {
    // 0x90 клавиша NumLock
    _hook = new Hook(0x90);
    _hook.KeyPressed += new KeyPressEventHandler( _hook_KeyPressed );
    _hook.SetHook();
  }
 
  void _hook_KeyPressed( object sender, KeyPressEventArgs e ) {
    MessageBox.Show("Is pressed.");
  }
}

void _hook_KeyPressed(object sender, KeyPressEventArgs e)
{
    switch (this.WindowState)
    {
        case FormWindowState.Normal:
            WindowState = FormWindowState.Minimized;
            break;
        case FormWindowState.Minimized:
            WindowState = FormWindowState.Normal;
            break;
    }
 
    keybd_event(0x9, 0x45, 0x1, (UIntPtr)0);
 
    //Сюда что-то нужно вставить...
}