hotcopy dump and incremental tar backups

Hi there,

I would like to make a daily incremental backup via tar gzip of a mysql
database. Therefore I do perform a hotcopy command first which gives me
a directory:
backup.20070417.incremental/databasename
The next day it looks like this:
backup.20070418.incremental/databasename

The tar command looks like this:
tar czP --listed-incremental=/home/www/logs/tar-inc-backup-FXDB.dat
--file=$BACKUP/FXDB-i-$NOW-$i.taz $BACKUP/databasename

Unfortunatelly it creates always a full backup since the directory is
not the same due to the date.

Has anybody an idea how to solve this and create incremental backups of
the database?

Thank you for any help!

Merlin