Код:

#include "windows.h"
#include <process.h>
BYTE buff[5];

bool SetSplicingHook(void* pfnDst, void* pfnHook, BYTE buffer[5])
{
	if(IsBadWritePtr(buffer, 5) || IsBadReadPtr(pfnDst, 5)) return false;
	memcpy(buffer, pfnDst, 5);
	DWORD old = 0;
	if(!VirtualProtect(pfnDst, 5, PAGE_READWRITE, &old)) return false;
	
	DWORD offset = (DWORD) pfnHook - (DWORD) pfnDst - 5;
	*(BYTE*)pfnDst = 0xE9; // JMP FAR
	*(DWORD*)((DWORD)pfnDst+1) = offset;

	if(!VirtualProtect(pfnDst, 5, old, &old)) return false;


	return true;
}

bool UnsetSplicingHook(void* pfnDst, BYTE buffer[5])
{
	DWORD old = 0;
	if(!VirtualProtect(pfnDst, 5, PAGE_READWRITE, &old)) return false;
	memcpy(pfnDst, buffer, 5);
	if(!VirtualProtect(pfnDst, 5, old, &old)) return false;
	return true;
}

void destroy()
{
	HMODULE DllHandle = GetModuleHandle(TEXT("engine.dll"));
	FARPROC Addr = GetProcAddress(DllHandle,"SomeProgramHandle");
	if(Addr == NULL)
	{
		exit(0);
	}
	UnsetSplicingHook(Addr, buff);
}
void Reply() // функция которой заменяю
{
        destroy(); //Установка родной функции 
        .........
}

extern "C" __declspec(dllexport) void init(void)
{
	HMODULE DllHandle = GetModuleHandle(TEXT("some.dll"));
	FARPROC Addr = GetProcAddress(DllHandle,"SomeProgramHandle");
	if(Addr == NULL)
	{
		exit(0);
	}
	if(!SetSplicingHook(Addr, Reply,buff))
		exit(0);
	DisableThreadLibraryCalls(GetModuleHandle(NULL));
}

BOOL    WINAPI   DllMain (HANDLE hInst, ULONG ul_reason_for_call,LPVOID lpReserved)
{
	init();
	return true;
}