Binding content of contentPresenter in UserControl?

I've got a UserControl which is a modified toggleButton.

I've added two String properties to it so I can change (or bind) them in blend, which I want to be the text displayed when the button is toggled. ie when checked, one string is displayed, when unchecked - the other.

Setting the text is fine, and toggling the UserControl is fine, but I don't know how to set the content of the contentpresenter from a property of the toggle by a trigger. Here's a rough look at the code:

<UserControl
    x:Name="UserControl"
    <UserControl.Resources>
        <Style x:Key="BiTextToggleButtonWithBorder" TargetType="{x:Type ToggleButton}">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type ToggleButton}">
                        <Grid>
                            <Path x:Name="path" 
                                Data="M28,0.5 L28.071953,0.50129622 28.092436,0.5 115.90756,0.5 C117.89162,0.50000113 119.5,2.5147196 119.5,5.0000013 L119.61492,36.460156 119.61432,36.857203 C117.1338,37.367692 108.82679,39.239366 106.37993,47.492391 L44.667,47.5 28.092436,47.5 4.9999995,47.5 C2.5147185,47.5 0.5,45.485283 0.5,43 L0.5,21 0.51801485,20.64324 0.5,20.0835 C0.5,9.2678322 12.812169,0.50000072 28,0.5 z"
                                Stretch="Fill"
                            <ContentPresenter 
                                x:Name="contentPresenter" 
                                Content="{Binding}"/>
                        </Grid>

                        <ControlTemplate.Triggers>
                            <Trigger Property="IsChecked" Value="True">
                                <Setter Property="Content" TargetName="contentPresenter" Value="{Binding whatgoeshere!?}"/>
                            </Trigger>
                            <Trigger Property="IsChecked" V开发者_开发问答alue="False">
                                <Setter Property="Content" TargetName="contentPresenter" Value="whatgoeshere!?"/>
                            </Trigger>
                        </ControlTemplate.Triggers>

                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </UserControl.Resources>

    <Grid x:Name="LayoutRoot">
        <ToggleButton
            x:Name="ToggleButton"
            Style="{DynamicResource BiTextToggleButtonWithBorder}"
            FontSize="18.667"
            Foreground="{DynamicResource WhiteText}"/>
    </Grid>
</UserControl>

I can't even find the property I want to change. I've done similar bindings to objects within a UserControl before, but nothing that is in a style and in a controlpresenter.

What am I missing?

have you tried changing the {Binding} to a {TemplateBinding} ? (MSDN documentation here)