Access inner element in the ControlTemplate

Here goes my code:

<ControlTemplate TargetType="{x:Type ToggleButton}">
    <Border x:Name="Chrome">
        <Grid x:Name="Arrow">
            <Grid.Background>
                <DrawingBrush Viewport="0,0,4,4" Viewbox="0,-0.4,16,16" ViewboxUnits="Absolute">
                    <DrawingBrush.Drawing>
                        <GeometryDrawing x:Name="ArrowDrawing">
                            <GeometryDrawing.Geometry>
                                <PathGeometry>
                                    <PathFigure StartPoint="1,1" IsClosed="True">
                                        <LineSegment Point="2,2.45"/>
                                        <LineSegment Point="3,1"/>
                                        <LineSegment Point="2,1.75"/>
                                    </PathFigure>
                                </PathGeometry>
                            </GeometryDrawing.Geometry>
                        </GeometryDrawing>
                    </DrawingBrush.Drawing>
                </DrawingBrush>
            </Grid.Background>
        </Grid>
    </Border>
    <ControlTemplate.Triggers>
        <Trigger Property="IsEnabled" Value="False">
            <Setter Property="Brush" TargetName="ArrowDrawing" Value="{StaticResource DisabledForecolor}"/>
        </Trigger>
    </ControlTemplate.Triggers>
</ControlTemplate>

So when the trigger triggers (on compile time), I got the error:

Cannot find the Trigger target 'ArrowDrawing'. (The target must appear before any Setters, Triggers, or Conditions that use it.)

How do I actually access that GeometryDrawing named ArrowDrawing from the trigger?

This post might help

There is a way to solve this, though, by using data binding. With a Binding, you can find your way out of the brush to an element, and then the Setter can target that element.