C / C++ / MFC

// ASDClock.cpp : Defines the entry point for the DLL application.
//

#include "stdafx.h"
#include "winuser.h"

HANDLE hInstance;
HHOOK hhookHooks;
const int WH_KEYBOARD = 2;

BOOL APIENTRY DllMain( HANDLE hModule, 
                       DWORD  ul_reason_for_call, 
                       LPVOID lpReserved
					 )
{

	hInstance = hModule;
	switch (ul_reason_for_call)
	{
	case DLL_PROCESS_ATTACH:
	case DLL_THREAD_ATTACH:
	case DLL_THREAD_DETACH:
	case DLL_PROCESS_DETACH:
		break;
	}

    return TRUE;
}

int HookSystem(int AddressOfCallBackFunction);
int UnHookSystem(int HookID);

int HookSystem(int AddressOfCallBackFunction)
{
	hhookHooks = SetWindowsHookEx(WH_KEYBOARD, 
		                          (HOOKPROC) AddressOfCallBackFunction,
								  (HINSTANCE) hInstance,
								  0);
	return (int)hhookHooks;
}

int UnHookSystem(int HookID)
{
	int iResult = 0;
	iResult = UnhookWindowsHookEx((HHOOK)HookID);
	if (iResult == 0) return 0; else return 1;
}

Public Declare Function HookSystem Lib "D:\Lucru\Test\ASDClock.dll" (ByVal AddressOfTheCallBackFunction As Long) As Long
Public Declare Function UnHookSystem Lib "D:\Lucru\Test\ASDClock.dll" (ByVal HookID As Long) As Long

Public Function KeyboardCallback(ByVal Code As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
   MsgBox Code
End Function

Dim test As Long
test = HookSystem(AddressOf KeyboardCallback)

LIBRARY ASDClock
DESCRIPTION "Testing some hook."
EXPORTS
HookSystem @1
UnHookSystem @2