[flexcoders] Load Tree Icon at Runtime

[Shaun]

I'm trying to load a tree icon at runtime (don't want to embed because 
it will have already been cached by the browser before the flex app).  
I have a function like:

private function treeIcon(item:Object):Class
{
    if (item is CustomObjectVO)
    {
        ????
    }
}

I can't seem to figure out what to replace ???? with.  I've tried 
various ways of using an Image control, but the tree expects a type of 
Class and I can't seem to make that happen.

Any thoughts?
Thanks,
Shaun