LED Sequential Lighter

Hi, I need to build a ciruit that is like this.

When IR LED 1 is blocked, I want LED 1 to glow.
When IR LED 2 is blocked, LED 1 nad LED 2 should glow.
" " 3 " " 1,2,and 3 " "
" " 4 " " 1,2,3 and 4 " "
..
..
..
..


Also want to calculate the rate of motion from(using) the time lag b/w
LED 1 and LED 2(or any two adjacent LEDs), and calculate the time
it will take for LED 8 to be blocked, and display the time on a
seven segment display.

Also I need to display the distance b/w 2 LEDs(and hence the volume),
on another display.

Please Help me if you have any ideas.