access method from template in wpf - wpf

Question

I'm using WPF with the caliburn micro framework to implement a MVVM pattern.
I've created a popup that gets filled with custom buttons inside a ListBox.
Now I want to call a method in my ViewModel when one of these buttons is clicked, but each approach I tried so far failed.
Here the code in comments works in the sense that it calls my method, but the parameter is always null.
<ListBox x:Name="lst" ItemsSource="{Binding OperatingModes}" ItemTemplate="{DynamicResource DataTemplate_Level1}" BorderThickness="0" ScrollViewer.CanContentScroll="False" ScrollViewer.HorizontalScrollBarVisibility="Disabled" ScrollViewer.VerticalScrollBarVisibility="Disabled">
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<UniformGrid Columns="3" />
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
<!--<i:Interaction.Triggers>
<i:EventTrigger EventName="PreviewMouseLeftButtonDown" >
<cal:ActionMessage MethodName="SelectMode">
<cal:Parameter Value="{Binding ElementName=lst, Path=SelectedItem}" />
</cal:ActionMessage>
</i:EventTrigger>
</i:Interaction.Triggers>-->
</ListBox>
And this is the Template I'm using. Whenever I call this method, I'm getting "No target found for method SelectMode." As you can see, I've tried different aproaches, although I'm not sure that I used the TargetWithoutContext call properly.
As far as I can tell I need to somehow bind my template to the data context of the "normal" xaml code, but I failed so far. How do I access my method properly?
<DataTemplate x:Key="DataTemplate_Level1" x:Name="myListTemplate" >
<ListBox ItemsSource="{Binding}" BorderThickness="0" ScrollViewer.CanContentScroll="False" ScrollViewer.HorizontalScrollBarVisibility="Disabled" ScrollViewer.VerticalScrollBarVisibility="Disabled">
<StackPanel Orientation="Vertical" HorizontalAlignment="Center" cal:Bind.Model="{Binding}" cal:Action.TargetWithoutContext="{Binding DataContext, ElementName=lst}">
<Button Style="{StaticResource InformButton}" Content="{Binding Path=Name}" FontSize="11" BorderBrush="BlueViolet" cal:Message.Attach="SelectMode($dataContext)">
<!--<i:Interaction.Triggers>
<i:EventTrigger EventName="MouseRightButtonDown" >
<cal:ActionMessage MethodName="SelectMode">
<cal:Parameter Value="{Binding ElementName=myListTemplate, Path=SelectedItem.Name}" />
</cal:ActionMessage>
</i:EventTrigger>
</i:Interaction.Triggers>-->
</Button>
</StackPanel>
</ListBox>
</DataTemplate>