Adding ondelete_callback to tl_member [SOLVED]

I'm still trying to get some sort of callback or hook going so that when I delete a FE member FROM THE BACKEND, another module will be purged of related data.
I've given up on the closeAccount hook, as this only works with a members self-deletion using the FE closeAccount module.

So now I'm trying to add an ondelete_callback to tl_member.php from myModule, but I can't get that to work either.

Can anyone see the reason why this doesn't work?

In myModule/dca/tl_member.php

Code:

---

//add an ondelete_callback to the tl_member module
$GLOBALS['TL_DCA']['tl_member']['config']['ondelete_callback'] = array('tl_joblistings_members', 'resetAfterMemberDelete');

---

In myModule/dca/tl_joblistings_members.php

Code:

---

class tl_joblistings_members extends Backend
{
        public function resetAfterMemberDelete(Datacontainer $dc)
        {
        $thememberno = "callback worked";
       
                $this->Database->prepare("UPDATE tl_joblistings_members SET company =? WHERE memberno =115")
                ->limit(1)
                ->execute($thememberno);       
        }
}

---

My problem was that my class was extending Backend, and should have been extending tl_member instead