Amigo, olha aqui !
http://msdn.microsoft.com/en-us/library/windows/desktop/ms680553(v=vs.85).aspx
Um exemplo de código:
HWND hwnd = FindWindow("tibiaclient", NULL);
DWORD processId;
HANDLE tibia;
if(!hwnd)
return 0;
GetWindowThreadProcessId(hwnd, &processID);
tibia = OpenProcess(PROCESS_VM_READ, false, processId);
if (!tibia)
return 0;
char buffer[32];
ReadProcessMemory(tibia, (HEX ADDR), &buffer, sizeof(buffer), 0);
std::cout << buffer << std::endl;
CloseHandle(tibia);