I'm also trying to get this working. As it is now, I have two popups, one of which is activated through the other and is essentially a 'page 2' of the first.
What I've done is added a 'next' button to the first page that has the following actions:close previous ui open new ui (page 2)
This works however it isn't not cosmetically pleasing.
I will probably need to resort to python to get things working smoothly.