Adding values from single select option after randomizing

how can we add values of different single select question after randomizing using the traditional flash cards approach,
For question choice1: rnd==1
For question choice2: rnd==2
For question choice3: rnd==3
For question choice4: rnd==4
Since only one of the variables may be holding a value but we want to have them summed up in one variable. Can we do this before exporting the data? what expression can we use?
i have refereed this before

Perhaps, something like this should be written as an expression for the sum variable:
choice1??0 + choice2??0 + choice3??0 + choice4??0

But do check how you are doing the flashcards. Randomization like you quote is useful when the respondent is doing self-enumeration, such as in web interviews. When doing a face-to-face interview the respondent looks at the flash card, tells the applicable options, interviewer marks them in tablet. No need to reshuffle the options for the interviewer.

Best, Sergiy Radyakin