Custom validation Data Binding

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WPF

Hi everybody,

I have this XAML

<Window x:Class="_2nd_DataBindingTest.CustomValidation"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:Valid="clr-namespace:_2nd_DataBindingTest.Validation"
        Title="CustomValidation" Height="300" Width="300">
    <Grid>
        <Grid.Resources>
            <ControlTemplate x:Key="ValidationTemplate2">
                <Border BorderBrush="Red" BorderThickness="5" CornerRadius="7">
                    <AdornedElementPlaceholder />
                </Border>
            </ControlTemplate>
        </Grid.Resources>
        <!--This is an implementation of a custom validation with a Regex
        using the general validation rule in the code behind and pass the parameters here in XAML-->
        <Label Content="Email:" HorizontalAlignment="Left" Margin="10,10,0,0" VerticalAlignment="Top"/>
        <TextBox HorizontalAlignment="Left" Height="23" Margin="59,14,0,0" TextWrapping="Wrap"
                 VerticalAlignment="Top" Width="223" Name="txtCV">
            <TextBox.Text>
                <Binding Path="Email" UpdateSourceTrigger="LostFocus">
                    <Binding.ValidationRules>
                        <Valid:RegexValidation x:Name="rgv"
                            Expression="^([\w-\.]+)@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.)|(([\w-]+\.)+))([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$"
                            ErrorMessage="Email is not valid!" />
                    </Binding.ValidationRules>
                    <Binding.ValidatesOnDataErrors>True</Binding.ValidatesOnDataErrors>
                </Binding>
            </TextBox.Text>
            <TextBox.Style>
                <Style TargetType="TextBox">
                    <Style.Triggers>
                        <Trigger Property="Validation.HasError" Value="True">
                            <Setter Property="ToolTip" Value="There is an error!" />  <-----
                        </Trigger>
                    </Style.Triggers>
                </Style>
            </TextBox.Style>
        </TextBox>
        <CheckBox Content="CheckBox" HorizontalAlignment="Left" Margin="10,42,0,0" VerticalAlignment="Top"/>


    </Grid>
</Window>

I would like to know how to bind the value of the marked line to the ValidationRule's ErrorMessage property.

I thought about a Binding with a RelativeSource=self, but I'm stopped here. Any ideas?