Forum OpenACS Q&A: do you Really REALLY *REALLY* want to do this?

We're just wrapping up a project (built on ACS4) that has a lot of important functionality in popups, including the sort of thing you describe here - you have no idea how much you don't want to go down that path... Unless your client (you?) is absolutely set on it, I'd suggest not trying to retrofit that sort of interface onto ACS.

If you're set on it, I can offer some suggestions to do what you're after, but it won't be elegant by any stretch of the imagination.