Synchronize the size of controls that lay in different ItemsCollections - wpf

Question

I want to synchronize the width of two controls.
<!--DataContext-->
<DockPanel LastChildFill="True" x:Name="HeaderDockPanel">
<DockPanel LastChildFill="True" MinHeight="60" DockPanel.Dock="Top" DataContext="{Binding Month}" d:DataContext="{d:DesignInstance Type=local:Month}" >
<TextBlock Text="{Binding Name}" Style="{StaticResource TitleTextBlock}" DockPanel.Dock="Left" />
<!--this shoud to set the Width-->
<!--Nested_1 DataContext Model_1-->
<local:DaysLine HorizontalAlignment="Left" Width="{Binding ElementName=HeaderDockPanel, Path=DataContext.DaysHeaderWidth, Mode=TwoWay}" />
</DockPanel>
<!--Nested_1 DataContext Model_2-->
<ListView Grid.Row="1" ItemsSource="{Binding CarBusiness}">
<ItemsControl.ItemTemplate>
<DataTemplate >
<DockPanel d:DataContext="{d:DesignInstance Type=local:CarBusiness}" LastChildFill="True">
<TextBlock Text="{Binding Name}" Style="{StaticResource TitleTextBlock}" DockPanel.Dock="Left" Margin="-6 0 0 0"/>
<!--this shoud to get the Width-->
<!--Nested_2 DataContext Model_3-->
<ItemsControl ItemsSource="{Binding Business}" Style="{StaticResource HorizontalItemsControl}" Width="{Binding DaysHeaderWidth}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<Grid />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<local:BusinessTextBlock d:DataContext="{d:DesignInstance Type=local:Business}" Business="{Binding}" ColumnWidth="20" HorizontalAlignment="Left" />
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</DockPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ListView>
</DockPanel>
The problem is that i can't find the source by RelativeSource Binding use FindByName.
The target control whatch on nested DataContext that is an item of the first and i cant set it in without adding to all this models the MyWidth property.
Is there a some enother way to bind them more correct?
I am thinking about a static property but it is not as correct as i want because i have planned to have a several instances of this control.