Getting dates from observablecollection

Question

Hi,

I have a ObservableCollection bound to a Dockpanel. This collection holds some data, and one of the members is a datetime field.

Now, i have created a calendar-control which requires a ObservableCollection of DateTime. Is it possible to get/make an ObservableCollection from the dockpanel?

Let me show some xaml to make it a bit more clear:

<UserControl x:Class="MyApp.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:Convertor="clr-namespace:MyApp.Convertors" 
xmlns:View="clr-namespace:MyApp.Views.WorkItems"
xmlns:ViewModel="clr-namespace:MyApp.ViewModel.WorkItems"
MinHeight="100" MinWidth="100">

<!-- resources -->
<UserControl.Resources>
    <Convertor:StatusConverter x:Key="statusConverter" /> 
    <Convertor:FormattingConverter x:Key="formattingConverter" />

    <!-- the view model -->
    <ViewModel:Model x:Key="viewModel" />

</UserControl.Resources>

<!-- main dockpanel with the viewModel as datacontext -->
<DockPanel DataContext="{StaticResource viewModel}">

       <!-- 
           SelectedDates is a public ObservableCollection<DateTime>,
           How would i get all the "plannedDates" as a collection? without (!) using the codebehind ?
       -->
       <View:Calendar SelectedDates="" />

       <ListBox ItemsSource="{Binding Items}">
            <ListBox.ItemTemplate>
                  <DataTemplate>
                      <TextBlock Text="{Binding Description}" />
                      <TextBlock Text="{Binding PlannedDate}" />
                  </DataTemplate>
            </ListBox.ItemTemplate>
       </ListBox>
       <!-- etc -->
</DockPanel>

Thanks in advance! steve