Border for some cells of a grid in WPF

add Border inside Grid with correct Grid.Column, Grid.Row and Grid.RowSpan attributes:

<Grid Grid.Column="1">
    <!--row definitions, columns definitions, controls-->

    <Border BorderThickness="1" BorderBrush="Green" 
            Grid.Column="2" Grid.Row="2" Grid.RowSpan="2"/>
    <Border BorderThickness="1" BorderBrush="Green" 
            Grid.Column="4" Grid.Row="3" Grid.RowSpan="2"/>
</Grid>