dataobject : problem with insert function

Hi,

I would like redefine insert function because I need to set the key value.
But Dataobject ignore the value that I give it.
Here's the function :

function insert(){

DB_DataObject::DebugLevel(1);

$this->rubcode=81;


parent::insert();


}



Normally, I should have 81 for the insert value, really, I have the value 9,
dataobject does not take into account my value. What have I to do?