Has anyone had any success in creating the n-back task in medialab?

Here is what I would like to do. I would like to present a list of numbers on the screen, one at a time, for a set amount of time (say 5 minutes). All the person has to do is hit a button, preferably the space bar, if the current number listed one that was presented 2 screens ago (the 2-back task).

The problem I face is this. I wanted each number to say on the screen for 2 seconds (regardless if they answer or not) then move onto the next number. I also want to know where medialab stops the person in the list (since the overall time is fixed for 5 minutes).

Anyone have any type of experience with this or have any ideas on how to do this?

If you have already successfully created the n-back task with medialab please contact me)!