WPF re-evaluate style triggers - wpf

Question

My App supports Localization in English and Spanish. I have a textlabel that depending on the property Age it applies different styles.
For example, if Localization is set to English:
If Age < 18 -> Text = Under age [in colour red]
If Age > 18 -> Text = Over age [in colour green]
If Age == 18 -> Text = On eighteen [in colour blue]
This is working fine with this code:
<TextBlock Margin="5,0,0,0">
<TextBlock.Style>
<Style TargetType="{x:Type TextBlock}">
<Style.Triggers>
<DataTrigger Binding="{Binding Path=Age,
Converter={StaticResource CuttoffConverter}, ConverterParameter=18}"
Value="False">
<Setter Property="Text" Value="{Loc strUnderAge}"/>
<Setter Property="Foreground" Value="Red"/>
</DataTrigger>
<DataTrigger Binding="{Binding Path=Age,
Converter={StaticResource CuttoffConverter}, ConverterParameter=18}"
Value="True">
<Setter Property="Text" Value="{Loc strOverAge}"/>
<Setter Property="Foreground" Value="Green"/>
</DataTrigger>
<DataTrigger Binding="{Binding Age}" Value="18">
<Setter Property="Text" Value="{Loc strOnEighteen}"/>
<Setter Property="Foreground" Value="Blue"/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
The localization part, is covered with {Loc XXXXXX} tag and it works fine except for this: if the language is changed "on-air", this DataTrigger Setter properties are not re-evaluated, so the labels are still displayed in English.
Is there any way to force to be re-evaluated?
UPDATE:
I have updated my Localization library to this one: WPF Localization Advanced which now supports Styles.
However, now it breakes when compiling the above XAML code. The error says:
"LocExtension is not valid for Setter.Value. the only supported
MarkupExtension types are DynamicResoruceExtension and BindingBase or
derived types."
Is there any way to accomplish the same purpose I did with trigger but with any of the suported methods by LocExtension?

Answer 1

define strUnderAge as a property within a class that Implements the INotifyPropertyChanged Interface.
bind the trigger to the strUnderAge property.
when you change the language raise the PropertyChanged event.
Otherwise the trigger can not know that the language has changed.