[Lynne]

It's unclear to me whether you are asking the user to set this field or whether you are going to write code to determine this field. If you are going to ask the user, then just use a profile field (you said you tried, but couldn't, so tell us exactly what you did and what the result was), if you are going to write some code to do it, one way would be to create a new column in the user table, add that column into the validfields for the user datamanager (class_dm_user.php), and then use the datamanager to save the information for you upon registration.