How do I use a listbox that has a checkbox that comes from a different source?

I'm got a problem that's really got me stumped. I want to have a ListBox on a page. The ItemsSource for that list box I want bound to a lookup table. I'll display a description field from the lookup table. That's all a fine and good; not hard to do.

What makes it harder is that I want to add a checkbox to each row in the listbox. Each checkbox is either checked, or not, if there's a value stored in another table (a data table) corresponding to the ID value from the lookup table, which is in the data table as a foreign key to the lookup table. I've written a value converter, but believe me this is getting way too complicated, and ultimately I don't think this is going to work. Here's the C# for the value converter:

[ValueConversion(typeof(byte), typeof(bool))]
public class ClientProbConverter : IValueConverter
{
	public int ClientNumber { get; set; }
	public byte CaseNumber { get; set; }
	public byte AdlProblem { get; set; }

	#region IValueConverter Members

	public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
	{
		byte adlProblem = (byte)value;
		bool ret = false;

		ASIEntities asiContext = new ASIEntities();

		var asiAdlProblem = asiContext.ASIADLProblems.Where(c => c.ClientNumber == ClientNumber && c.CaseNumber == CaseNumber && c.ADLProblem == adlProblem).FirstOrDefault();

		if (asiAdlProblem != null)
		{
			ret = true;
		}

		asiContext.Dispose();

		return ret;
	}

	public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
	{
		bool tmp = (bool)value;

		ASIEntities asiContext = new ASIEntities();
		var asiAdlProblem = asiContext.ASIADLProblems.Where(c => c.ClientNumber == ClientNumber && c.CaseNumber == CaseNumber && c.ADLProblem == AdlProblem).FirstOrDefault();

		if (tmp)
		{
			if (asiAdlProblem == null)
			{
				var prob = new ASIADLProblem();
				prob.ClientNumber = ClientNumber;
				prob.CaseNumber = CaseNumber;
				prob.Followup = 0;
				prob.ADLProblem = AdlProblem;
				asiContext.ASIADLProblems.AddObject(prob);
				asiContext.SaveChanges();
			}
		}
		else
		{
			//the checkbox was cleared
			if (asiAdlProblem != null)
			{
				asiContext.DeleteObject(asiAdlProblem);
				asiContext.SaveChanges();
			}
		}

		asiContext.Dispose();

		return AdlProblem;
	}

	#endregion
}

As you can see, I have 3 public properties to this ClientProbConverter class: ClientNumber, CaseNumber and AdlProblem. All 3 comprise the primary key of the data table, with ADLProblem being the foreign key to the lookup table. ASIEntities is an entity framework class I wrote for fetching/saving the data to the database. I had hoped that I could somehow bind ClientNumber, CaseNumber and ADLProblem, from the data table, to the check box in each row of the list box, but I'm not sure I can.

Here's the XAML for the listbox:

<ListBox x:Name="listOfProblems" Grid.Row="1"
					HorizontalAlignment="Left"
					AllowDrop="True"
					FontSize="16"
					ItemsSource="{Binding Source={StaticResource aSICodesADLProblemViewSource}}"><ListBox.ItemTemplate><DataTemplate><Grid><Grid.ColumnDefinitions><ColumnDefinition Width="200" /><ColumnDefinition /></Grid.ColumnDefinitions><TextBlock Text="{Binding ADLProblemDesc}" /><!-- the next textblock will eventually be hidden --><TextBlock Grid.Column="1" Text="{Binding ADLProblem}" /></Grid></DataTemplate></ListBox.ItemTemplate></ListBox>

aSICodesADLProblemViewSource is the CollectionViewSource for the lookup table. ADLProblemDesc and ADLProblem, in this context is coming from the lookup table (ASICodesADLProblem). I want to add a checkbox to this listbox, which will be related to the data table (ASIADLProblems in the EF context), but I'm completely stumped as to how to do it, and I honestly think what I've got so far is too complicated and doesn't do the job. How do I accomplish what I'm trying to do? Or should I approach this differently?

---

Rod