Functional index in 9.30 not used for range search

Hi All, We are trying to implement case-insensitive searches in a 9.30 database, running on Windows 2000. I have created an uppercase() function to use with the index: create function uppercase(x varchar(255)) returning varchar(255) with ( not variant ); return upper(x); end function; We have a table called "individual", which has a column "surname". I have created (among others) the following index, and updated statistics (high did not make a difference): create index individual_1 on individual(uppercase(surname)); update statistics for table individual; The test data for this table contains about 100,000 records.