Hi @ENCDIGITAL,
You could do this by using a simple constraint or a regex code as outlined below.
In the survey tab of your xlsform:
Data entry screen as seen in Enketo: When a wrong entry is made
Data entry screen as seen in Enketo: When a correct entry is made
Reference xlsform:
Number Constraint.xlsx (9.7 KB)
If you wish to learn more on handling constraint, please feel free to have a look at our support article Limiting Responses with Validation Criteria. Similarly you could also have a look at our support article Restricting text responses with regular expressions to learn more about regex.
Have a great day!
