look:
[highlight=cpp]void MemWrite(DWORD Addr, PBYTE Buffer, SIZE_T Len)
{
DWORD oldProtection = NULL;
VirtualProtect((LPVOID)Addr, Len, PAGE_EXECUTE_READWRITE, &oldProtection);
memcpy((LPVOID)Addr, Buffer, Len);
VirtualProtect((LPVOID)Addr, Len, oldProtection, NULL);
}[/highlight]
Edit, if you want to use this to a game, then I strongly recommend you to do not. it is proolly detected.