Thanks for the reply. That's actually exactly what I'm doing, and it's working great except for the scrollbar issue. I don't understand why in Flex, expanding a tree by a function call works different than the built in expansion that's called when the user clicks the expand node on the tree. I haven't been able to find what the difference is but there must be one because it behaves differently.
Unfortunately, I can't find any other way to expand the tree that will make the scrollbar activate, and I also haven't found any way to activate the scrollbar by a refresh. The only thing that works is for a user to click the expand node on the tree, but without knowing that, the users just can't see the rest of the tree that is below the bottom of the box.