rsync - Apr 2009 - Only backup deleted files/dirs

I am missing a option for --backup
By default --backup copies deleted and changed files. With patching
rsync I can specify a dir for the deleted files and a dir for the
changed files.
My problem is that I don't care abotu changed files/dirs. Only deleted
files/dirs are interesting.
Is there any workaround or option that I can use to only backup deleted
files/dirs?

Telling --backup-dir to use /dev/null did not work :)

Greetings

Jens Grieger