Aren't you basically asking to be able to provide a multitasking feature within your single process that uses as much `leftover time` as is available for background tasks and doesn't get in the way of the important stuff you need to accomplish? Why not just do the stuff you must get done at the start of the frame then with remaining time just do a loop where you do a bunch of background stuck and check the Millisecs() every now and then to see if the frame time has run out yet?