Binding Fill property to value of node with particular id in XML

Hi there, I have this XML file:

<?xml version="1.0" encoding="utf-8"?>
<Wpf>
<wpfctrl id="NavBtnTemplate">#FFCFDEFF</wpfctrl>
</Wpf>

and i want to bind Fill property of My Rectangle to value of wpfctrl node with id="NavBtnTemplate". How I can achieve this? Actually I have this rectangle inside my custom UserControl's Control Template. But hope that will not be the problem since I can bind to the properties of elements inside UserControl:
My UserControl (actually is very simple)

<UserControl.Resources>
<ControlTemplate x:Key="WpfWebSparkNavTemplate" TargetType="{x:Type Button}">
<Grid x:Name="controlLayout" Height="29.648" Width="84.284">
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CommonStates">
<VisualState x:Name="Normal"/>
<VisualState x:Name="MouseOver"/>
<VisualState x:Name="Pressed"/>
<VisualState x:Name="Disabled"/>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Rectangle x:Name="rectangle"Fill="#FFCFDEFF" Margin="0" Height="31" d:LayoutOverrides="VerticalAlignment" >
</Rectangle>

<Label x:Name="buttonCaption" VerticalAlignment = "Center"
HorizontalAlignment = "Center"
FontWeight = "Bold" FontSize = "12" Content="{TemplateBinding Content}"/>
</Grid>
</ControlTemplate>
</UserControl.Resources>

I did not found Blend wizard to allow me to state such filters on XML

Please help. Thank you.