Restrict the response base on a possible empty question (the answer for this question might be empty)

[Kal_Lam]

@manh_nguyen, you should be able to do it as outlined in the image shared below:

In the survey tab of your XLSForm:

Data entry as seen in Enketo: when date 2 is smaller than date 1

Data entry as seen in Enketo: when date 2 is equal to date 1

Data entry as seen in Enketo: when date 2 is greater than date 1

Reference XLSForm:

Constraint Date.xlsx (9.7 KB)