Access EditorArea Overflow with Javascript

So this is a strange one. I've actually dealt with it before, but not in conjunction with FCKEditor and it's superb but highly nested structure.

THE PROBLEM

In FF2, when using a javascript lightbox-style popup like Slimbox, Multibox, or Thickbox, the scrollbars in the parent page are still active. Meaning, that they're not in the background or disabled...you either have to disable them in the javascript (set overflow to hidden when lightbox is active, etc.) or you have to position your actual lightbox so they avoid them...lest the scrollbar sit RIGHT ON TOP of your picture or whatever you're popping up. I've been able to address this problem before (not using FCKEditor) with a line of script like this:

document.getElementById('main-scroll').setStyles({'overflow': 'hidden'}); (Where 'main-scroll' is the div with the scroller)

IN RELATION TO FCKEditor

So, after spending several hours hunting through the forums looking for any ID or other signifier for the editor area itself--and specifically the part that scrolls, I HAVE been able to track down the place that's actually doing the overflowing. In fck_editorarea.css, the HTML element can be set to overflow: hidden and voila, the scroller disappears. I don't, however, know how to target this element with Javascript.

And hey...I'll admit my novice. I do know, however, that it will have to start with some sort of ID or path within the page, and that's where I'm trying to start. If ANYBODY can help, I'd appreciate it.

===

ADDENDUM

One thing I have noticed, also, is that--in spite of all my experience with various lightbox scripts--the FCK dialogs (Image, Link, Etc.) somehow lay OVER scrollbars. I'd imagine that this has to do with some sort of fantastic iframe or some other such wizardry, but I can't locate the script that enacts the overlay to investigate further. I'd be open to pursuing this course of action if someone out there thought it was better/faster/easier.

Thanks much in advance.