Next button to appear after all layers have been viewed?

I haven't been able to to have the Next button only appear after all layers have been viewed, but I have used triggers and states so that the Next button will only go to the next slide only under certain conditions.

The way I got this to work was to put some shapes off the slide in the same number as layers, and when a layer is opened it changes the state of one of those shapes to visited. Then I add conditions to the next button trigger so that it will only work if all of those shapes are in the visited state.

i also like to have a character or text tell the person using the tool that the next button won't work until they have viewed all the info, otherwise they might get confused or think it isn't working properly.

I hope this helps, and I hope even more that someone has a better suggestion than I do, I'm sure there is a more sophisticated way of doing it.!