Log in as an admin Enable conditional activities if you haven't already. Enter a course and enable conditional activities. Add a new forum and in the settings: Check that you can add user conditions and that all the conditions strings are fine (equals, is empty, contains etc). Check you see an "is not empty" option Set a single new user condition for the "Yahoo ID" field and set the condition to "is not empty" Log out and back in as a student. Make sure the user hasn't got a yahoo id set (who would right!) Browse to the course Make sure the forum is shown as inaccessible with a message about yahoo id being empty.