Hello! I've about 250 survey respondents. Each one has his/her own unique code (attributed by me to them offline). I've, as first question in my survey, a question named "unique code", which has to be from 1 to 250. If a respondent enters "3" as his own unique code, and by mistake a second respondent, after some time, enters "3" this last value has to be rejected because it is a duplicate. Is there any built-in function that will allow me to perform this test? Is there any example I can use to test against the survey database previous entries? Many thanks in advance! E