Passing Expansion properties of matrix report to "Jump To" matrix report

I'm dealing w/ SSRS 2005.
I have my main matrix report which has two textboxes that act as expansion/collapse "objects" for the fourth and fifth row groups.
On my column headers, I have a navigation "jump to" report.
How can I pass to this "jump to" report the boolean (or whatever) property that either my 4th or 5th (or both) row groups were expanded and now my jump to" report has the same thing.
I was going to use a report parameter for this, but when you go to "Edit Group/Visibiltiy", the "Visibiltiy can be toggled by another report item" doesn't even list parameters...just text boxes.
Basically, the goal is that whatever the user has expanded on the main report, the "jump to" report will have the same expansions.
Thanks!