Change Xaml Pages

I have a xaml page that has a ContentControl that has a Grid. That Grid houses another xaml file. I am wondering how to change the Xaml page withing that Grid to something else. I want to change it from within that Grid, but I can't figure it out.

Here is what I would look like:

<UserControl...>

<Grid...>

<ContentControl...>

<Grid>

Switch Xaml within this Grid FROM within this grid.

</Grid>

</ContentControl>

</Grid>

</UserControl>

 

 Its kinda hard to explain, so if you have any questions, let me know. Thanks.
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