arduino working delay - do things while delay is called rather than wait.

working_delay

// Used instead of delay so various things can still be checked (e.g. button presses, saving data).
int workingDelay(int interval) {

	unsigned long previousMillis = millis();
	while(true) {

		unsigned long currentMillis = millis();
		Serial.println(currentMillis);
		// If the current miliseconds run is more than the interval, the delay has been done, so exit.
  		if(currentMillis - previousMillis > interval) {
			return 0;
		} else {
			// running during delay
			int randNum1 = random(300);
			int randNum2 = random(300);
			int randNumSum = randNum1 + randNum2;
			Serial.println("Sum result:");
			Serial.println(randNumSum);
			// end running during delay
		}
	}

}