Blacklight Expander problem while expanding programmatically

I am doing a silverlight project in Silverlight 4 and I included the BlackLight project in my project so that I could use their new controls, especialy the dockpanel and th开发者_如何学运维e autoexpander, which is causing me at the moment some little problems.

What I would like to do is to have several auto-expander that will expand or collapsed when I click on button. In my case more specifically, each auto-expander have a set of parameter to fill, which in turn will fill the other expander and the current one would collaps and the just filled one would expand.

The idea is simple, yet when I use a button which is on one of my expander, it only works once... It would expand/collapse the first time, then after that, nothing. I trace the code and it seems to go through just fine, but the property value won't change

Here is my code

 Private Sub BtnExpand_Click(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles BtnExpand.Click
        ClientExpander.IsExpanded = False
        ProjetExpander.IsExpanded = True
    End Sub

Could it be a known bug, or must I reset some flags to make it work?

Edit : Forgot to mention, if it makes any difference, but the IsExpanded property seems to be a dependancy property. Thanks.