Vista - Why is this so difficult (Template question)

Hello all,

I'm trying to do something that I thought would be simple with wpf.
Basically, I want to create a template that sticks a TextBlock on the
end of a ComboBox.

The idea is that when my forms are in "edit" mode that the required
fields are marked with a red asterisk. While I've figured out how to
do this with a textbox:

<Style x:Key="RequiredEditableTextBox" TargetType="{x:Type
TextBox}">
<Setter Property="Control.Template">
<Setter.Value>
<ControlTemplate
x:Key="RequiredEditableTextBoxTemplate" TargetType="{x:Type TextBox}">
<StackPanel Orientation="Horizontal">
<TextBox Text="{TemplateBinding Text}"/>
<TextBlock Style="{StaticResource
RequiredFieldGlyph}"/>
</StackPanel>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
I'm mystified as to how one would accomplish this with a more complex
control like a combobox.

What I really want is a template that refers to the parent control,
essentially saying "Draw yourself here"

<Style x:Key="RequiredEditableComboBox" TargetType="{x:Type
ComboBox}">
<Setter Property="Control.Template">
<Setter.Value>
<ControlTemplate
x:Key="RequiredEditableComboBoxTemplate" TargetType="{x:Type
ComboBox}">
<StackPanel Orientation="Horizontal">
---I WANT TO DRAW THE ORIGNIAL COMBOBOX HERE
--
<TextBlock Style="{StaticResource
RequiredFieldGlyph}"/>
</StackPanel>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

But I can figure out how. The difficulty I'm having leads me to
believe that I may be thinking of the problem in the wrong context
etc.

Any ideas would be appreciated.

Thanks

-r