NBack task

Hi all,

I've been trying to adjust the 2-Back task in Psytoolkit library to a 3-Back task, but I'm having lots of trouble with figuring out how to do this. I'm a bit of a novice with Psytoolkit coding and it's a bit over my head! I know it has to occur somewhere here:

## if a 2back trial
if $memory == 1 and &trialcount > 2
set $currentletter &nback2
set $requiredresponse 1 ## the m key needs to be pressed later, m=stands for Memory
set $typeoftrial 1
fi
## if a NON n-back trial
if $memory != 1 or &trialcount <= 2 ## chose a letter but not that of 3 trials ago
set $currentletter random 1 15
while $currentletter == &nback2 ## choose anything but NOT that of 3 back
set $currentletter random 1 15
while-end
set $requiredresponse 0 ## no key should be pressed
set $typeoftrial 0
fi

...but I know there's also some changes I have to make with the feedback to line it all up. Can anyone help? Thanks!