Retrieve final render size of rowheader of datagrid WPF

Class MainWindow
    Private data As New ObjectModel.ObservableCollection(Of Object)()
    Public Sub New()
        InitializeComponent()
        For i As Integer = 0 To 999
            data.Add(New With{.Column1=$"Row {i}",
                              .Column2=$"Value {i}{vbNewLine}JUST FOR FUN",
                              .Column3=$"Data {i}"})
        Next i
        WPF001.ItemsSource = data
    End Sub
End Class

<Window x:Class="MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:RowHeaderFinalRenderSize"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <DataGrid x:Name="WPF001" AutoGenerateColumns="True"
            HorizontalAlignment="Center" VerticalAlignment="Top"
            Width="780" Height="307" Margin="0,10,0,0"/>
        <Label x:Name="lb" BorderThickness="1" BorderBrush="Black" Margin="325,368,325,10"
               Content="{Binding ElementName=WPF001, Path=RowHeader.RenderSize.Height, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
    </Grid>
</Window>