Mc Brain, thanks for the tip on the S-Grid but that is not the issue I'm trying to pursue here.

You are correct to state that the individual controls in Outlook Express are a ListBox and/or TreeView, but these controls occupy the window in different "frames"... such that between them there is a spine. When the cursor moves over the spine the cursor changes to a double-ended arrow and the user can resize these "frames". Perhaps a better term than "frame" would be a "pane"... in keeping with the "windows" analogy.

Thanks for the help.