#define THREADS_NUMBER_A 10
#define THREADS_NUMBER_B 4
DWORD dwThreadsId[THREADS_NUMBER_A];
HANDLE hThread;

// Создаем потоки в количестве THREADS_NUMBER_A
for(int i=0; i<THREADS_NUMBER_A; i++) {
    CreateThread(0, 0, (PTHREAD_START_ROUTINE)TestThread, 0, 0, &dwThreadsId[i]);
}
    
// Убиваем THREADS_NUMBER_B потоков
for(int i=THREADS_NUMBER_A-1; i>=THREADS_NUMBER_A-THREADS_NUMBER_B; i--) {
    hThread = OpenThread(THREAD_TERMINATE, 0, dwThreadsId[i]);
    TerminateThread(hThread, 0);
}