How can I set a default value in DBDOFB?

Hi all: I have a table where one of the fields it´s the link to another table: class DO_Subtiposinmueble extends DB_DataObject { ###START_AUTOCODE /* the code below is auto generated do not remove the above tag */ public $__table = 'subtiposinmueble'; // table name public $codsubtipo; // int(11) not_null primary_key public $nombre_es; // string(30) public $nombre_en; // string(30) public $numBusquedas; // int(11) public $codtipo; // int(11) /* Static get */ function staticGet($k,$v=NULL) { return DB_DataObject::staticGet('DO_Subtiposinmueble',$k,$v); } /* the code above is auto generated do not remove the tag below */ ###END_AUTOCODE } The field $codtipo it´s a field that I need to set the value when I get the form with DBDOFB. In the way that this value is sent to the database directly. How can I do it? Thank you in advanced. Regards, Jose Manuel Zea