Disabling Next Button w/out Timeline Pausing

I'm stumped and wonder if anyone has any ideas.

I have a slide with four boxes that are triggered to branch to different slide sequences of 3-4 each. After viewing those, clicking NEXT returns the learner to my main menu slide. 

Here's my problem. I want the NEXT button on the main menu slide disabled until they've clicked on every box, and have triggers to disable it when the timeline starts, then change it to normal when the boxes' states are all visited. But since they are leaving the slide and then returning, the timeline is restarting and thus re-disabling the NEXT button, even though the trigger is based on the boxes' state being VISITED. 

I don't want to lightbox my branches, because the text is too small in lightboxes. I think my next solution is to create a custom "NEXT" button that can just have an initial state of HIDDEN, but for consistency's sake, I like them to use the normal NEXT button. So I wondered if anyone had any ideas I hadn't thought of.

TIA!