如何获得相对于向导的控制边界

I hope I can explain my problem. I am working on a dialog that can contain number of trees from left side, and one tree from right side. I need to draw a line from left to right, but for some reason, I am getting the same tree item bounds. For example, when the first item is selected in tree one it will return the same bounds location for the first item in tree two. How do I get item bounds relative to the wizard and not to the composite.I hope I can explain my problem. I am working o