That depends on what he needs the list of new processes for. If it is for something as simple as highlighting new processes in a listing, he wouldn't care about processes that have already exited.

However, the only way I can see of making sure you'd see every process, no matter how fast it exited, is by some sort of a callback that would be triggered by process creation. Perhaps the Win32 API offers that, I don't know. But that's not the question that was asked.