How can I multbinding in Caliburn.Micro

Question

Good Morning,

I'm trying to use the code below with Caliburn.Micro, but I can't seem to get it to work without this Window.DataContext...

 <Window.DataContext>
    <viewmodel:MainWindowViewModel />
</Window.DataContext>

<Window.Resources>       
    <converter:LookupConverter x:Key="LookupConverter" />
    <Style x:Key="CalendarDayButtonStyle" TargetType="CalendarDayButton">            
        <Style.Triggers>
            <DataTrigger Value="True">
                <DataTrigger.Binding>
                    <MultiBinding Converter="{StaticResource LookupConverter}">
                        <Binding />
                        <Binding Path="DataContext.HigligthDates" RelativeSource="{RelativeSource AncestorType=Calendar}" />
                    </MultiBinding>
                </DataTrigger.Binding>
                <Setter Property="Background" Value="Pink" />
            </DataTrigger>
        </Style.Triggers>
    </Style>
</Window.Resources>

I tried:

 <MultiBinding Converter="{StaticResource LookupConverter}">
         <Binding />
         <Binding Path="HigligthDates" RelativeSource="{RelativeSource AncestorType=Calendar}" />
 </MultiBinding>

or

  <MultiBinding Converter="{StaticResource LookupConverter}">
     <Binding />
     <Binding x:Name="HigligthDates" RelativeSource="{RelativeSource AncestorType=Calendar}" />

I get this error: https://i.stack.imgur.com/v76k2.png

However none of this worked. Does anyone know what I should do in order for Caliburn.Micro to perform this job?