I need function that can get time for less than a second

I have to make a runtime analysis of quicksort and selection sort. For this, i need to determine the average runtime of sorting 100 integers. I tried using clock() and time() but i think these return time in seconds. The program however takes less than a second so the value returned is 0. what else can I use?

If you're allowed to include windows.h, you can use GetTickCount(), which returns the number of milliseconds since windows started.
Run it two times and calculate the differemce.