Updating a control without interrupting

Question

I saw the post http://www.c-sharpcorner.com/uploadfile/835123/cross-thread-operations-in-C-Sharp/  that allows me to update a control using a new thread, but it still makes the program wait for the thread to complete.  why is that?  can't i constantly update a control without interrupting the rest of the program?  for example, how could i make the listbox in that post count upward constantly but be able to do anything else i want to at the same time?