private void ScrollViewer_PreviewMouseWheel(object sender, MouseWheelEventArgs e)
{
	if (sender is ListBox && !e.Handled)
        {
		e.Handled = true;
		var eventArg = new MouseWheelEventArgs(e.MouseDevice, e.Timestamp, e.Delta);
		eventArg.RoutedEvent = UIElement.MouseWheelEvent;
		eventArg.Source = sender;
		var parent = ((Control)sender).Parent as UIElement;
		parent.RaiseEvent(eventArg);
	}
}

<Window x:Class="TestProject.MainWindow"
                xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
                xmlns:local="clr-namespace:TestProject"
                Title="MainWindow" Height="350" Width="525">
    <Grid Margin="0,0,0,20" x:Name="rootGrid">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>

        <Button Grid.Row="0" Command="{Binding ToggleCmd}">Toggle Last Name Visible</Button>
        <CheckBox Grid.Row="1" IsChecked="{Binding IsLastNameVisible}">Is Last Name Visible</CheckBox>

        <telerik:RadMultiColumnComboBox Grid.Row="2">
            <telerik:RadMultiColumnComboBox.ItemsSourceProvider>
                <telerik:GridViewItemsSourceProvider ItemsSource="{Binding AllClubs}" AutoGenerateColumns="false" >
                    <telerik:GridViewItemsSourceProvider.Columns>
                        <telerik:GridViewDataColumn DataMemberBinding="{Binding FirstName}"   />
                        <telerik:GridViewDataColumn DataMemberBinding="{Binding LastName}"
                                                    IsVisible="{Binding DataContext.IsLastNameVisible , ElementName=rootGrid}" />
                    </telerik:GridViewItemsSourceProvider.Columns>
                </telerik:GridViewItemsSourceProvider>
            </telerik:RadMultiColumnComboBox.ItemsSourceProvider>
        </telerik:RadMultiColumnComboBox>

    </Grid>
</Window>

public class CustomGridViewItemsSourceProvider : GridViewItemsSourceProvider
{
	protected override Freezable CreateInstanceCore()
	{
		return new CustomGridViewItemsSourceProvider();
	}
}

this.mccb.AddHandler(RadMultiColumnComboBox.PreviewMouseLeftButtonUpEvent, new MouseButtonEventHandler(Mccb_MouseLeftButtonUp), true);
//---------------
private void Mccb_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
	var button = Mouse.DirectlyOver as RadDropDownButton;
	if (this.mccb.IsDropDownOpen && button != null && button.TemplatedParent is RadMultiColumnComboBox)
	{
		Dispatcher.BeginInvoke(new Action(() => { button.CaptureMouse(); }));
	}
}

private void RadMultiColumnComboBox_Loaded(object sender, RoutedEventArgs e)
{
	var mccb = (RadMultiColumnComboBox)sender;	
	var tb = mccb.FindChildByType<TextBox>();
	tb.Text = string.Empty;
}