Restrict combination with select_multiple type of question


I'm Coding an XLSform and I want to limit the combinations of a select_multiple question. all choices are of type "text". let's take this exemple:

Q1-How long did you stay there?

  1. Less than a week
  2. Between two and four weeks
  3. Between two and three months
  4. Between four and six months
  5. Between seven and twelve months
  6. More than a year
  7. Do not know

The surveyor can select among different choices, but if he selects the answer 7 "Do not know" he won't be able to select any other choices. So basically any combinations is possible from the moment when answer 7 is not ticked. Of course the surveyor can pick only the answer 7 and go to the next question.

Thank you a lot.

Please take a look at Don't allow other options to be selected with Don't Know

Thanks a lot Hélène !