Digit Span Backwards

Does anyone know how to make the Digit span task test backwards? For instance, if they give you the numbers '7-0' you would input '0-7' to be correct. I can't find a proper code anywhere, and I'm not sure what changes I would have to make in the code below. 


options
mouse on
bitmapdir stimuli
scale

fonts
normalfont arial 18
bigfont arial 28

bitmaps
digit1 # 1
digit2
digit3
digit4
digit5
digit6
digit7
digit8
digit9
digit0 # 10
##
continue_button
continue_button_dark ## for after being clicked
clear_button
mask
# -- instructions ------------
i1
i2
i3
i4
backButtonImage
nextButtonImage
startButtonImage

## important variables:
## &spancounter : the number of trials WITHIN a span (maximally 3)
## &spancorrect : the number of correct trials WITHIN a span (maximally 2, need 2 to continue)
## &actualspan : the max number someone remembered

######################################################

task digittask ## starts with 2 and then goes up every correct 2
## Step 1: Create random number sequence
set &&allNumbers range 1 10 ## from the bitmaps
set &&numberSequence sample &testspan from &&allNumbers
## Step 2: Start screen with basic instruction to get ready
font bigfont ## use big font for following two texts
show text "Memorize digits" #1
delay 1000
clear -1
show text "Get ready now!" #2
delay 800
clear -1
font normalfont ## back to smaller font for rest of texts
## Step 3: show all digits at 800 ms per digit
set $tmp_counter 1
while $tmp_counter <= &testspan
show bitmap &&numberSequence[$tmp_counter] #3
delay 800 ## how long each to-be-memorized digit will be shown
clear -1
set $tmp_counter increase
while-end
#
# Step 4: show the possible clickable digits and other buttons
#
show bitmap continue_button 250 250
set $range_begin show-counter
show bitmap clear_button -250 250
set $clear_counter show-counter
#
show bitmap digit1 -150 -250
show bitmap digit2 0 -250
show bitmap digit3 150 -250
#
show bitmap digit4 -150 -160
show bitmap digit5 0 -160
show bitmap digit6 150 -160
#
show bitmap digit7 -150 -70
show bitmap digit8 0 -70
show bitmap digit9 150 -70
#
show bitmap digit0 0 20
#
show rectangle 0 100 350 5 255 255 0 ## vertical "line", looks nice
#
set $range_end show-counter
#
# Step 5: Now let participant click the digit sequence from memory
#
set &&mask_stimuli clear ## for keeping track of masks overlayed on stimuli in virtual keyboard
set &&range_array range $range_begin $range_end ## so that we can later remove already clicked items from it
set &&digits_chosen clear
set &&already_done clear
while $finish_selection == 0 ## loop until continue button clicked
readmouse l 1 99999 range &&range_array
set &&rts append RT ## store for later save
set &&clickedStimuli append UNDER_MOUSE ## store for later save
if UNDER_MOUSE == $range_begin ## continue button was clicked
set $finish_selection 1
show bitmap continue_button_dark 250 250 # cover over continue button
show bitmap continue_button_dark -250 250 # cover over clear button
fi
if UNDER_MOUSE == $clear_counter ## clear button clicked
set $position_counter decrease 1
set $last_digit &&digits_chosen remove last
set $tmp &&range_array_removed remove last ## these values were stored
set &&range_array append $tmp ## increase range array
## now remove last mask drawn and last digit underneath
set $last_mask &&mask_stimuli remove last
set $last_digit &&digitsUnderStimNums remove last
clear $last_mask
clear $last_digit
fi
if UNDER_MOUSE > $clear_counter ## a digit button was clicked
set $position_counter increase
set &&range_array remove value UNDER_MOUSE ## remove so it cannot be clicked again
set &&range_array_removed append UNDER_MOUSE ## the removed values need to be saved in case you want to undo this action ("clear")
set $clicked_stimulus_x getx UNDER_MOUSE
set $clicked_stimulus_y gety UNDER_MOUSE
show bitmap mask $clicked_stimulus_x $clicked_stimulus_y ## mask the digit
set $tmp_mask show-counter
set &&mask_stimuli append $tmp_mask ## keep track of the mask stimuli in case removal needed
## now show red circle on the digit button that was clicked
show circle $clicked_stimulus_x $clicked_stimulus_y 20 255 100 100
delay 100
clear -1
##
set $myIndex expression UNDER_MOUSE - $clear_counter ## this makes the digits go from 13 to 22
## was this digit clicked before
set $already_done &&digits_chosen locate $myIndex ## check if digit was already clicked before
if $already_done == 0 ## if not already clicked (each digit is only used once in sequences)
set &&digits_chosen append $myIndex
set $xPosDigits expression $position_counter * 60 - 300
show bitmap $myIndex $xPosDigits 150
set &&digitsUnderStimNums append SHOW_COUNTER
fi
fi
while-end
#
# Step 6: Save detailed trial data
#
save BLOCKNUMBER "rts" &&rts
save BLOCKNUMBER "clickedStim" &&clickedStimuli
#
# Step 7: digit entry done, check if sequence was entered correctly
#
if &&digits_chosen == &&numberSequence
set $error_status 0
save BLOCKNUMBER &best_so_far &testspan $error_status "//" &&numberSequence "//" &&digits_chosen
set &spancorrect increase
show text "CORRECT" 0 70
if &spancounter < 3
set &spancounter increase
fi
if &spancorrect == 2
set &spancounter 0
set &spanerror 0
set &spancorrect 0
set &best_so_far &testspan
set &testspan increase
fi
fi
if &&digits_chosen != &&numberSequence
set $error_status 1
save BLOCKNUMBER &best_so_far &testspan $error_status "//" &&numberSequence "//" &&digits_chosen
set &spanerror increase
if &spancounter < 3
set &spancounter increase
fi
show text "WRONG" 0 70
fi
delay 2000
set &&clickedStimuli clear
set &&rts clear
#
# end task when 2 errors in row
#
if &spanerror == 2
set &digitspan &testspan
end tasklist
fi
# end task when digitspan is going to 11
# this is unlikely to happen, though
if &testspan == 10
end tasklist
fi

######################################################################
## blocks
######################################################################

block training
pager option mouse backButtonImage -250 220 nextButtonImage -30 220 startButtonImage 250 220
pager i1 i2 i3
set &testspan 2
tasklist
digittask 1
end

block digit_block
message i4 mouse
set &testspan 2
set &spancorrect 0
set &spanerror 0
set &spancounter 0
tasklist
digittask 99
end
feedback
text 0 -200 "Your memory score is the sequence you could remember 2x in a row."
text 0 -100 &best_so_far ; prefix "Your best sequence (digit span): "
text 0 100 "Click the mouse anywhere to continue"
wait_for_key mouse
end