Access to a special frame from diverse pages

Question

request: changing Inhalt.Source from the page 'page2.xaml' (Button-Click). I don't find any possibility

to access Inhalt.Source inside of page2

<Grid>

<Frame Grid.Column="0" Name="Inhalt" Source="page1.xaml" />
<Frame Grid.Column="1" Source="page2.xaml" />
...