Stopping people from moving on

I have developed a system simulation where the user must complete each step before they are able to move on to the next page.On those steps, I simply disinherit the course's main next button, paste a copy of the next button on the page and set the "initially visible" property unchecked. When the user completes the activity, I set an action that sets the button to visible. They can then continue to the next page normally.The only drawback is that if they wanted to they could open up my table of contents and move on. If you don't include a TOC, you wouldn't have that problem.Hope this helps,Chris