dynamic sizing of a tree object and an iframe within a frame

I am developing a web based help system.

The application is a java app which sit on the left side of a frame.

On the right side of the frame are two object vertically stacked.

One is a AW tree object and beneath it an iframe.

When yo click on a tree leaf, the html associated with that leaf appears in the iframe.

I would like to have the tree and iframe dynamically size themselves.
for example. As I expand the tree, the iframe shrinks vertically
As I contract the tree, the iframe expands vertically

Any body have any ideas??