unit Unit1;

interface

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

const
  MY_MESSAGE = WM_USER + 1;

type
  TForm1 = class(TForm)
    Memo1: TMemo;
    btnSetHook: TButton;
    btnUnsetHook: TButton;
    procedure btnSetHookClick(Sender: TObject);
    procedure btnUnsetHookClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
    { Private declarations }
    procedure MyHandler(var msg: TMessage); message MY_MESSAGE;
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

const
  DLLName = 'myhook.dll';

type
  Tsetthehook = procedure(Handle: HWND);stdcall;
  Tdelthehook = procedure;stdcall;

var   setthehook:TSetthehook;
      delthehook:TDelthehook;
      DLLInstance : THandle;

Procedure loadlib;
begin
    DLLInstance := LoadLibrary(DLLname);
    if DLLInstance = 0 then ShowMessage('Cannot Load DLL')
    else
    begin
      @setthehook := GetProcAddress(DLLInstance, 'SetTheHook');
      @delthehook := GetProcAddress(DLLInstance, 'DelTheHook');
    end;
end;

procedure TForm1.btnSetHookClick(Sender: TObject);
begin
  SetTheHook(Handle);
end;

procedure TForm1.btnUnsetHookClick(Sender: TObject);
begin
  DelTheHook;
end;

procedure TForm1.FormCreate(Sender: TObject);
var
  Resstrm: TResourceStream;
begin
  Resstrm := TResourceStream.Create(HInstance, 'MYDLL',RT_RCDATA);
  Resstrm.SaveToFile(ExtractFilePath(Application.ExeName) + DLLname);
  Resstrm.Free;

  loadlib;
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  FreeLibrary(DLLInstance);
  DeleteFile(ExtractFilePath(Application.ExeName) + DLLname);
end;

procedure TForm1.MyHandler(var msg: TMessage);
begin
  Memo1.Lines.Add(IntToStr(msg.WParam) + ' disabled ...');
end;

end.