ComboBox selection change breaks DataTrigger - wpf

Question

I am trying to set the selected value of a combobox from a style trigger.It works as long as we dont manually change any value in the combobox.But it stops working altogether after manually changing the selection.How can i solve this.A sample code is attached.Please do help
<Window x:Class="InputGesture.Window2"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:InputGesture"
Title="Window2" Height="300" Width="300" Name="Sample">
<Window.Resources>
<Style TargetType="{x:Type ComboBox}">
<Setter Property="ComboBox.SelectedValue" Value="1"/>
<Style.Triggers>
<DataTrigger Binding="{Binding ElementName=chk,Path=IsChecked}" Value="True">
<Setter Property="ComboBox.IsEnabled" Value="False"/>
<Setter Property="ComboBox.SelectedValue" Value="2"/>
</DataTrigger>
</Style.Triggers>
</Style>
</Window.Resources>
<StackPanel>
<CheckBox Name="chk" Height="23"/>
<ComboBox Name="cmb" Height="23" DisplayMemberPath="Name"
SelectedValuePath="Id" ItemsSource="{Binding ElementName=Sample,Path=DT}">
</ComboBox>
<Button Height="23" Click="Button_Click"/>
</StackPanel>
</Window>

Answer 1

I have found a Quick but Dirty Solutuin i guess..If anyone has a better Idea Please..
<Window x:Class="InputGesture.Window2"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:InputGesture"
Title="Window2" Height="300" Width="300" Name="Sample">
<Window.Resources>
<Style TargetType="{x:Type ComboBox}">
<Style.Resources>
<Storyboard x:Key="valueStoryBoard" >
<ObjectAnimationUsingKeyFrames Duration="00:00:00"
FillBehavior="HoldEnd"
Storyboard.TargetProperty="SelectedValue">
<DiscreteObjectKeyFrame KeyTime="00:00:00"
Value="{x:Null}" />
<!--<DiscreteObjectKeyFrame KeyTime="00:00:00"
Value="2" />-->
</ObjectAnimationUsingKeyFrames>
</Storyboard>
</Style.Resources>
<Style.Triggers>
<DataTrigger Binding="{Binding IsChecked, ElementName=chk}"
Value="True">
<DataTrigger.EnterActions>
<BeginStoryboard x:Name="stb" Storyboard="{StaticResource valueStoryBoard}" />
</DataTrigger.EnterActions>
<Setter Property="ComboBox.IsEnabled" Value="False"/>
<DataTrigger.ExitActions>
<StopStoryboard BeginStoryboardName="stb" />
</DataTrigger.ExitActions>
</DataTrigger>
</Style.Triggers>
</Style>
</Window.Resources>
<StackPanel>
<CheckBox Name="chk" Height="23"/>
<ComboBox Name="cmb" Height="23" DisplayMemberPath="Name"
SelectedValuePath="Id" ItemsSource="{Binding ElementName=Sample,Path=DT}">
</ComboBox>
<Button Height="23" Click="Button_Click"/>
</StackPanel>
</Window>