RepeatableEntry state modification aren't possible?

return $infolist
    ->schema([
        // List all page views of the visitor session
        RepeatableEntry::make('pageViews')
            ->schema([
                // The page view path
                TextEntry::make('Path')
                    ->columnSpanFull(),

                // The duration of the visit for this page
                TextEntry::make('Duration')
            ])

            // Is this somehow possible?
            ->state(
                fn(Session $record) => $record->pageViews
                    ->map(fn(PageView $pageView, int $key) => [
                        'path' => $pageView->path,
                        'duration' => isset($record->pageViews[$key+1]) ? $pageView->created_at->diff($record->pageViews[$key+1]->created_at) : null
                    ])
            )
    ]);