Not able to fire events from WPF Combo box items after once item is selected?

There is a scenario i am trying to accomplish for quiet sometime, could not find the way to do with Combo Box. I have Combo box which has a DataTemplate containing a button and textblock. The button is bind to some event so when user clicks on it inside the combo box it fires an event. It works well until i make a selection once i selected the combo box item and than try to click button nothing happens. While doing selection button fires events, once i selecteditem from comb box where button is part of the individual item. Now when i try to click on button which is now a selecteditem of comb box it does not fire any event. Nothing happens.

I want the button to be clickable and fire event even when combo box item is in selected mode inside selectiobox. how can i do that? 

thanks

vj