<UserControl.Resources>

<Style>

...

<Setter.Value>

                    <ControlTemplate TargetType="{x:Type TextBox}">

                        <Themes:ListBoxChrome x:Name="Bd" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" RenderMouseOver="{TemplateBinding IsMouseOver}" RenderFocused="{TemplateBinding IsKeyboardFocusWithin}" SnapsToDevicePixels="true">

                            <Grid>

                                <Grid.ColumnDefinitions>

                                    <ColumnDefinition />

                                    <ColumnDefinition Width="Auto" />

                                </Grid.ColumnDefinitions>

                                <ScrollViewer Grid.Column="0" x:Name="PART_ContentHost" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>

                                <TextBlock Grid.Column="1" Margin="0,0,1,0" Text="cm" Foreground="Gray"/>

                            </Grid>

                        </Themes:ListBoxChrome>

                        <ControlTemplate.Triggers>

                            <Trigger Property="IsEnabled" Value="false">

                                <Setter Property="Background" TargetName="Bd" Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}"/>

                                <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>

                            </Trigger>

                        </ControlTemplate.Triggers>

                    </ControlTemplate>

                </Setter.Value>

...

</Style>

</UserControl.Resources>



<Grid>

        <TextBox Name="txt" Style="{DynamicResource TextBoxStyle1}"/>

    </Grid>

public static readonly DependencyProperty UnitNameProperty = DependencyProperty.Register("UnitName", typeof(string), typeof(TextBoxWithUnit), new PropertyMetadata("cm"));

public string UnitName

        {

            get { return GetValue(UnitNameProperty).ToString(); }

            set { SetValue(UnitNameProperty, value); }

        }