On MATLAB I am writing a code using if else functions. The user is supposed to enter a few inputs, however if they enter an INVALID input for one of the questions, the entire program should stop and ask no further questions.

How do I do that? What function should I use to make the program stop if the user enters and invalid input?

I CANNOT use the "return" function, this IS NOT A LOOP it is just if else statements. I have tried the "break" function, and "while" and they do not work. Please help.