Vista - Binding inside binding question

Hi,
I want to bind Text property of TextBox to a dictionary where key is a name of the TextBox. (I want to make a Style out of that and use it for a number of TextBoxes).

The binding does not work. (exception in debugger).
Can someone please advise ?



Here is my Xaml:
<Window
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2006" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" xmlns:LableList="clr-namespace:LableList"
x:Class="LableList.Window1"
x:Name="Window"
Title="Window1"
Loaded="WindowLoaded"
Width="640" Height="480">

<Grid x:Name="LayoutRoot">
<TextBox x:Name="QType">
<TextBox.Text>
<Binding Source="{x:Static Application.Current}"
Path="MainWindow.DataMap[{Binding RelativeSource={x:Static RelativeSource.Self}, Path=Name}].Data"/>
</TextBox.Text>
</TextBox>
</Grid>
</Window>



And here is the c# code:
namespace LableList
{
public partial class Window1
{
private Dictionary<string, Value> _DataMap = new Dictionary<string,Value>();
public Dictionary<string, Value> DataMap
{
get { return _DataMap; }
}
public Window1()
{
DataMap.Add("QType", new Value("QType", "aaaaa"));
this.InitializeComponent();
}
}

public class Value
{
public Value(string iName, string iData)
{
_Name = iName;
_Data = iData;
}
private string _Name;
public string Name
{
get { return _Name; }
set { _Name = value; }
}

private string _Data;
public string Data
{
get { return _Data; }
set { _Data = value; }
}

public override string ToString()
{
return Data;
}
}
}