How to prevent TreeListBox from exanding/contracting a node when double-clicking

Hi,

I am trying to implement something similar to the solution explorer in Visual Studio, and would like to "open" the associated document when the user double-clicks on a node.  My code (handling the OnItemDefaultActionExecuting event) seems to mostly work, but I have noticed that the tree also expands/contracts when the user double-clicks. 

Is there any way to prevent this, so that it works more like Visual Studio?

Thanks