Confirmation Window for RadCombobox.

[Shenbagaraj]

Hi im using RadComboBox in Silverlight 4. Im using  MVVM ,Riaservices prism for my application.
I need a a Confirmation window on selection change. The window should appear when user tries to chage the value in Combo box . If ok it should allow chane no it should not allow the user to change. What event i can use for it??
Using ASP.net i found events like OnClientSelectedIndexChanging, Using this event and JavaScript the are making it run

   I am not suppose to use Javascript and also i cont find SelectedIndexChanging  event like that.

Using Silverlight 4 how can i achieve this using MVVM pattern..
 my RadCombobox

<telerik:RadComboBox Name="comboboxMagazine"  MaxWidth="170"   IsFilteringEnabled="True" IsTextSearchEnabled="True" TextSearchMode="StartsWith" MinWidth="140" Grid.Row="1" Grid.Column="3" Height="20" DisplayMemberPath="MagazineName"
                  SelectedValuePath="MagazineID" ItemsSource="{Binding MagazineData,Converter={StaticResource AddEmptyItemConverter}}"
                  SelectedValue="{Binding JobRequest.MagazineID, Mode=TwoWay, UpdateSourceTrigger=Explicit, ValidatesOnDataErrors=True, ValidatesOnNotifyDataErrors=True, NotifyOnValidationError=True}">
                <i:Interaction.Triggers>
                    <i:EventTrigger EventName="SelectionChanged">
                    <ei:CallMethodAction MethodName="MagazineChanged"
                TargetObject="{Binding}" />
                    </i:EventTrigger>
                </i:Interaction.Triggers>
            </telerik:RadComboBox>