How to use TwoWay binding from within a UserControl?

I have my own UserControl, a `LabeledTextBox` which is the combination of a `Label` and a..well, `TextBox`. This Control has two properties: `Caption` which will be bound to the caption of the `Label`, and `Value` which will be bound to the `Text` of the `TextBox`. Code: ``` public class LabeledTextBox : Control { static LabeledTextBox() { DefaultStyleKeyProperty.OverrideMetadata(typeof(LabeledTextBox), new FrameworkPropertyMetadata(typeof(LabeledTextBox))); } public string Caption { get { return (string)GetValue(CaptionProperty); } set { SetValue(CaptionProperty, value); } } // Using a DependencyProperty as the backing store for Caption. This enables animation, styling, binding, etc... public static readonly DependencyProperty CaptionProperty = DependencyProperty.Register("Caption", typeof(string), typeof(LabeledTextBox), new UIPropertyMetadata("")); public string Value { get { return (string)GetValue(ValueProperty); } set { SetValue(ValueProperty, value); } } // Using a DependencyProperty as the backing store for Value. This enables animation, styling, binding, etc... public static readonly DependencyProperty ValueProperty = DependencyProperty.Register("Value", typeof(string), typeof(LabeledTextBox), new UIPropertyMetadata("")); } ``` XAML: ``` <Style TargetType="{x:Type local:LabeledTextBox}"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="{x:Type local:LabeledTextBox}"> <Grid> <Grid> <Grid.RowDefinitions> <RowDefinition /> <RowDefinition /> </Grid.RowDefinitions> <Label Grid.Row="0" Content="{TemplateBinding Caption}" /> <TextBox Name="Box" Margin="3,0,3,3" Grid.Row="1" Text="{Binding Value, RelativeSource={RelativeSource TemplatedParent}, Mode=TwoWay}" /> </Grid> </Grid> </ControlTemplate> </Setter.Value> </Setter> </Style> ``` Usage: ``` <uc:LabeledTextBox Caption="Code:" Value="{Binding ExpenseCode}" /> ``` Initially I thought I had found my answer here: WPF TemplateBinding vs RelativeSource TemplatedParent That details the difference between `TemplateBinding` and `RelativeSource TemplatedParent`. I've changed my code accordingly, but it still feels like I'm missing a step. The OneWay binding does work, my textbox is bound to the Value property, but changes do not register. How do I get this to work?