DynamicGrid.xaml

<Window 
       xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
       xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
       Title="WpfApplication1" Height="300" Width="300">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="*"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="Auto"/>
            <ColumnDefinition Width="*"/>
        </Grid.ColumnDefinitions>
        <Label Content="Left" Grid.Column="0" Background="LightBlue" />
        <GridSplitter 
                    VerticalAlignment="Stretch" 
                    HorizontalAlignment="Stretch"
                    Grid.Column="1"
                    Width="5" 
                    Grid.RowSpan="3"/>
        <Label Content="Right" Grid.Column="2" Grid.Row="2" Background="LightBlue" />
        <Label Content="Top" Grid.Column="2" Background="LightGreen"/>
        <GridSplitter 
                    HorizontalAlignment="Stretch"
                    VerticalAlignment="Stretch"
                    Grid.Row="1"
                    Width="Auto"
                    Height="5" 
                    Grid.ColumnSpan="3"/>
        <Label Content="Bottom" Grid.Column="0" Grid.Row="2" Background="LightGreen" />
    </Grid>
</Window>