get select record on relation manager attach form

->rule(static function (Forms\Get $get, Forms\Components\Component $component): Closure {
                                return static function (string $attribute, $value, Closure $fail) use ($get, $component) {

                                    $equipmentID = ;

                                    $existingRecord = DB::table('construction_has_equipment')
                                        ->where('serial_number', $value)
                                        ->where('equipment_id', $equipmentID)
                                        ->exists();

                                    if ($existingRecord) {
                                        $fail(__('construction-equipment.construction_equipment_resource.error'));
                                    }
                                };
                            }),