How to pass a procedure (implemented within a class) to a Win32 function?

Hi delphians,

I would like to pass a procedure which is implemented within a class to a
Win32 function.

I did it a few years ago but now I don't remember how.

Maybe some of you can help me.

If I put the procedure outside the class then I have no problem.
But I need to pass a procedure implemented within a class.

I have attached the code below.

Thanx and have a nice day

unit Form_Main;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Memo1: TMemo;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
    function EnumWindowsFunc (Handle: THandle; lParam: LPARAM): boolean;
stdcall;
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

function TForm1.EnumWindowsFunc(Handle: THandle; lParam: LPARAM): boolean;
begin
Result := True;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  Memo1.Clear;
  EnumWindows(@EnumWindowsFunc, 0) ;
end;

end.