If your minute-long process is running on the main thread, then it will block all UI updates regardless of using a timer or not. Put that process in a thread and use AddUserInterfaceUpdate to add rows to the listbox.
If your minute-long process is running on the main thread, then it will block all UI updates regardless of using a timer or not. Put that process in a thread and use AddUserInterfaceUpdate to add rows to the listbox.