How to avoid error text display when switched to a tab - wpf

Question

Based on the answer given in this question I am able to flash my error text.
<ControlTemplate x:Key="ErrorTemplate">
<StackPanel Orientation="Horizontal">
<AdornedElementPlaceholder x:Name="textBox"/>
<ItemsControl ItemsSource="{Binding}" VerticalAlignment="Center" HorizontalAlignment="Center">
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding ErrorContent}" Foreground="Red" Margin="5,0,0,0">
<TextBlock.Triggers>
<EventTrigger RoutedEvent="Loaded">
<BeginStoryboard>
<Storyboard>
<DoubleAnimation Storyboard.TargetProperty="Opacity" From="1" To="0" AutoReverse="False" Duration="0:0:0.5" RepeatBehavior="3x" />
</Storyboard>
</BeginStoryboard>
</EventTrigger>
</TextBlock.Triggers>
</TextBlock>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</StackPanel>
</ControlTemplate>
In my application there are number of tabs. The TextBlock is in one tab, the problem now I am facing is whenever I switch to this tab the ErrorText is flashing if it was previously shown. I think this is because I specify the RoutedEvent="Loaded". I want the error to be shown only if it is explicitly set again. Is there any way to achieve this using 'xaml` itself?
View model logic to specify the error string given below.
public string this[string columnName]
{
get
{
if (columnName == nameof(this.CurrentValue))
{
if (this.ShowErrorMessage)
{
return ValidationErrorMessage;
}
}
return null;
}
}