OnHelp Event Handler Demo 

unit HelpUnit;
interface
uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;
type
  TForm1 = class(TForm)
    Edit1: TEdit;
    Edit2: TEdit;
    Edit3: TEdit;
    procedure FormCreate(Sender: TObject);
    function TestHelp(Command: Word; Data: Longint;   var CallHelp: Boolean):
Boolean;
  private
    { Private declarations }
  public
    { Public declarations }
  end;
var
  Form1: TForm1;
implementation
{$R *.DFM}
procedure TForm1.FormCreate(Sender: TObject);
begin
 Application.OnHelp := TestHelp;
end;
function TForm1.TestHelp;
begin
 ShowMessage(Format('Command=%d; HelpContext=%d',[Command, Data]));
 CallHelp := False;
end;
end.