Hi! Im so sorry if someone already asked that (I did look for it but couldn't find), but I really need help with this.

Please, does anyone know how can I validate the result of a question based on the previous ones? I mean, I need the respondent to insert some purchase values in questions 1, 2 and 3, and in the 4th, the answer this respondent gives, need to be the total amount of those other 3. If not, the survey restarts. In all the cases, I will use an "open field" so this person types the prices of everything at each step.

If someone knows it, and can help me, it will be of great value for me!

Thanks!