unique vales

You can force it in the database (are you using MySQL?) but the error message you get back is not really user friendly. The other way is to put in some event code in to check before saving the record. From memory there have been other posts on this subject.

Using some of the code I found Jane had given someone else with a slight change it worked! of course you have to use your table name and field names.
ADD SCREEN event in the BEFORE RECORD ADDED:
global $conn;

$strSQLExists = "select * from tablename where fieldname='".$values["fieldname"]."'";

$rsExists = db_query($strSQLExists,$conn);

$data=db_fetch_array($rsExists);

if($data)

{

echo "<center><b><font color=red>Field name already exist</font></b></center>";

return false;

}

else

{

return true;

}