Setting Focus on a Control within a ControlTemplate in WPF

<Style TargetType="{x:Type controls:FieldTextBox}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type controls:FieldTextBox}">
                <Border BorderThickness="0" Margin="5">
                    <StackPanel ToolTip="{Binding Path=Field.HintText, RelativeSource={RelativeSource TemplatedParent}}">
                        <TextBlock Text="{Binding Path=Field.FieldLabel, RelativeSource={RelativeSource TemplatedParent}}"
                                   HorizontalAlignment="Left"
                                   />
                        <TextBox Width="{Binding Path=Field.DisplayWidth, RelativeSource={RelativeSource TemplatedParent}}"
                                 HorizontalAlignment="Left"
                                 Text="{Binding Path=Field.Data.CurrentValue, RelativeSource={RelativeSource TemplatedParent}}"
                                 IsEnabled="{Binding Path=Field.IsEnabled, RelativeSource={RelativeSource TemplatedParent}}"
                                 ContextMenu="{Binding Source={StaticResource FieldContextMenu}}" >
                            <TextBox.Background>
                                <SolidColorBrush Color="{Binding Path=Field.CurrentBackgroundColor, RelativeSource={RelativeSource TemplatedParent}}"/>
                            </TextBox.Background>
                        </TextBox>
                    </StackPanel>
                </Border>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
    <Setter Property="Focusable" Value="True" />
    <Setter Property="IsTabStop" Value="False" />
</Style>

Control control = (Control)this.Template.FindName("FocusableControl", this);
    if (control != null)
    {
        control.Focus();
    }