How do I bind to different datacontexts within the same usercontrol

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XAML

WPF

I have a ItemsControl whose Itemssource is bound to a collection of customWidgets as follows:

<ItemsControl ItemsSource ="{Binding MyCustomWidgets}">
 <ItemsControl.ItemTemplate>
  <DataTemplate>
   <CustomWidget Name="{Binding Name}" 
     SomeOtherDP="{Binding SomePropertyOfaCustomWidget}" 
     EditButtonCommand="{Binding   Path=MyButtonCommand,DataContext=MyViewModel}
   </CustomWidget>
  </DataTemplate>
 </ItemsControl.ItemTemplate>
</ItemsControl>

The ViewModel:
public class MyViewModel
	Inherits ViewModelBase
	public Property MyCustomWidgets as ObservableCollection(Of CustomWidget)
	   ... omitted for brevity    
        End Property
	
	Public Property MyButtonCommand as ICommand
	   ... omitted for brevity
	End Property
End Class

The Widget usercontrol has a button on it that is internally bound to a Custom Dependency property of type ICommand named EditButtonCommand

I want all properties of the Widget except the EditButton to bind to an instance of CustomWidget.
But I want the EditButton (i.e. the custom dependency property of the Widget) to bind to the MyButtonCommand Property of the same MyViewModel instance that the ItemsControl's datacontext is set to, not the CustomWidget.
It seems that I should be able to point the Button Binding to the datacontext of the ItemsControl (whose datacontext is set to the ViewModel) using some sort of relative ancestor verbage, but I can't figure out how to do this.
Does anyone know how to do this?