Please extend the recordset in Row_Inserting, Row_Updating etc. At the moment, the recordset ($rs, $rsold, $rsnew) contains only the keyvalues and not the lookup values.
For example the new structure could be like this:
$rsnew[month] = 1
$rsnew[lookup_month] = January
$rsnew[brand] = 4
$rsnew[lookup_brand] = Mercedes