I have a need to require users to fill out a set of questions within a repeat based on the answer to a question outside of the repeat. Is this possible? I've tried using the relevant field and creating a constraint without any luck.
Yes it's possible to apply expressions in the Relevant column for repeats.
We should be able to apply the expression to the repeat as a whole (hiding the repeat) or questions within the repeat. Here is more information on how to apply relevant expressions:
Constraints are a separate item, preventing users from submitting values unless the constraint is met.
If you're still encountering difficulty, can you please attach your XLSForm?
You need to use required. A constraint to check for a blank value does not work. So add the relevant then make the fields required. If it is hidden it will not fire the required.
Hope that helps