I have made some good progress with my ISR and am serial printing the count on the serial monitor, now what I want to achieve is to call the count to be displayed on my 3 digit seven seg cc display or rather let the ISR trigger the counts whenever the sensors flag depending on their sequence. I have the code to count from 0-999 back to 0 so my problem is how to combine with the ISR. Any help is much appreciated. Much thanks.