Forcing a checkmark before moving on

Hello,

I have read how to do this in Rise, but I need help on how to do this in Storyline. I have a disclaimer at the beginning of my course. I want the user to be forced to have the checkbox selected/checked in order for them to move on to the next slide.

Right now I have two triggers, "set checkbox to true when user clicks checkbox" "change state of next button to normal when user clicks checkbox if checkbox=true". However, a user could click on the checkbox, which changes the state of the next button normal, and then uncheck the checkbox before they select the next button. Therefore, someone could argue that they did not agree to the disclaimer but continued with the course.

So how can I force the the next button to not work unless the checkbox is selected/checked?