DBA Question - Finding out ACTUAL space used in 6.x

Are there any ORACLE 6.xx DBAs out there with utilities or ways to find out just how much space WITHIN an extent is actually being used? We are setting up a new database and are trying to evaluate the goodness of the table and index space calculation formulas we have used (from Chapter 16 of the DBA Manual). We have gone into the 2nd extent in some cases (especially for indexes where we didn't multiply the formula by 1.1 as suggested) but don't know by how much. It would be very helpful if we could somehow 'see inside' the extent to evaluate just how much we are off.

Thanks - and yes we know that ORACLE 7.xx will give us more DBA tools but won 't be able to convert for a while yet.

                                                            Janet Walker
Naval Command, Control and Ocean Surveillance Center, RDT&E DIV

    Code 0291, San Diego, California 92152 (619) 553-6838

                    MILNET: janet_at_nosc.mil