I want to have a field in my survey - just a simply short text field - that won't allow the user to enter a value if it has already been provided as an answer by someone else (same field, same survey, different users). The validation should NOT be case sensitive.
The survey is asking people's suggestions for names (animal rescue charity), so if they suggest a name that has already been suggested by another survey return it should not allow them to submit the survey until they change it.
Can this be done, and if so any suggestions as to how?