Restrict choices already selected for date fields

I'm new to ODK and have been reading a lot of the documentation and forum posts, but was hoping to get some help. I am working on a study that asks data collectors to enter a month/year in our study period, and then provide some additional information about a health facility during that month. They then need to do the same thing for another month in the study period. However, I'm noticing that I can select the same month for the second entry as I did for the first.

Is there a way to add a constraint or a choice filter to a date field (YYYY/MM)?

Thanks for any thoughts!

Welcome to the ODK forum, @sknudson! We're glad you're here. When you get a chance, please introduce yourself on this forum thread. I'd also encourage you to add a picture as your avatar because it helps build community!

This is possible using a constraint column and expression to validate the answer.

Here's an example: month_constraint.xlsx (9.0 KB)

Screenshot 2024-06-07 at 3.29.59 PM