如何在Flex中更改用于多选拖放操作的imagealpha

Here's the code that allows multi-select list to drag into a tree area. What I would like to do is to change the alpha of the image that gets dragged around. I've done some research but most of the discussions out there talk about how to change the dragged image. What I want to do is simply change the default alpha of the dragged item from 0.5 to say 0.2. Also this solution should be able to handle multiple select dragging. Thank you.Here's the code that allows multi-select list t