You can use the "validation" field. When creatig a question you can enter a
regular expression to check the data:
"This feature is available on all free text type questions ("Short Free Text", "Long Free Text", "Date" or "Numerical"
. You can use standard Regular Expressions in this field to validate the responses to the question, and if the responses don't validate against this expression, the user will be prompted to try again before they can progress."