Solvedsome help please :(

I've seen some tuts on mid function hooking if that's what it's called. Any ways i am trying it out and my target process is cheat engine's first tutorial.
but when i inject the dll and hit "hit me" the program crashes, i know it is something wrong with my hook length, and the assembly code. i would really appreciate it if some one can help me out here. all i want it to do is instead of sub let it add that's all

#include <iostream>
#include <Windows.h>
using namespace std;


void Hook(BYTE*original,DWORD dwMyFunc,DWORD dwLen) {

DWORD oldProtection;
DWORD newProtection;
DWORD relAddress;

VirtualProtect(original, dwLen, PAGE_EXECUTE_READWRITE, &oldProtection);

relAddress = (DWORD)(dwMyFunc - (DWORD)original) - 5;

*original = 0xE9;

*((DWORD*)(original + 0x1)) = relAddress;

for (DWORD x = 0x5; x < dwLen; x++) {
*(original + x) = 0x90;
}

VirtualProtect(original, dwLen, oldProtection, &newProtection);
}

DWORD jmpBackAddress;
void _declspec(naked) myfunc() {
__asm {
add eax, edx
mov dword ptr ds:[ebx+480], eax
jmp [jmpBackAddress]
}
}

DWORD WINAPI myThread(LPVOID lpParam) {
DWORD hookLength = 0x8;
DWORD original = 0x00423AFE;
jmpBackAddress = original + hookLength;
Hook((BYTE*)original, (DWORD)myfunc, hookLength);
FreeLibraryAndExitThread((HMODULE)lpParam, 0);
return 0;
}


BOOL WINAPI DllMain(HINSTANCE hModule, DWORD dwReason, LPVOID lpReserve) {
switch (dwReason) {
case DLL_PROCESS_ATTACH:
CreateThread(NULL, 0, &myThread, hModule, 0, NULL);
break;
case DLL_PROCESS_DETACH:
break;
case DLL_THREAD_ATTACH:
break;
case DLL_THREAD_DETACH:
break;
}
return 1;
}

Commenting with proper indentation of the OP. Next time include it in [code] tags to make it more readable.

Which part of the tutorial are you trying to hook? I'll take a look when I have a few spare minutes.

Set a breakpoint and step through your code, see where it stops working.