In this case, you will have to keep the "Copier Thread" running all the time. Put it on hold when all files in the list are copied. Use
System.Threading.AutoResetEvent.WaitOne();
for that in the Copier Thread.
In another thread, you can add a new path to your list and call
System.Threading.AutoResetEvent.Set();
. That will trigger the Copier Thread to resume until it has, again, reached the end of the list and enters the waiting state.
MSDN[
^] tells about the details.