Penny auction module

I write module for Penny auctions (similar to swoopo.com). Many things are finished, but I have problem with bid butlers (more details).

I has made one function that scanned all auctions and bid butlers in relation with that auctions. I need to run that function in background, because it will sleep when it has nothing to do. Something like

function function_name() {
  // Array with control signals.
  $bid_butlers = get_bid_butles();

  // Variable that save time of end of auction that will be first end.
  $first_end_time = get_first_end_time();

  while(true) {
    $signals = get_signals();
    if($signals['exit'] === TRUE) {
      break;
    }

    if($signals['rescan'] === TRUE) {
      // Rescan database for new auctions or bid butlers.
      $bid_butlers = get_bid_butles();
      $first_end_time = get_first_end_time();
    }

    if($first_end_time - time() < 10) {
      // Then start to place bids for auctions that have less than 10s to the end.

    }

    sleep(1);

  }
}

I don't know how to start that function in background. Maybe start function via cron will be solution, but I can't execute that function every second.