question about variables

I apologize if this question has already been asked but if I create a variable that will allow for the activation of the Next button after it reaches a specified number do I need to create a new variable for each slide on which I want to do this.

In other words, I want users to click 3 buttons on a given slide that will each reveal a layer with important information. After the variable reaches a specified value the user can click Next to see the next slide. If that number has not yet been reached they will get a warning they have to click on each of the buttons before they can proceed. Do I need to create a new variable for each screen or can I use one variable multiple times.

I'm assuming I need to create a new variable and proceeding on this assumption but thought I'd check with the community so for future course I might be able to save myself some effort. 

Have a wonderful Thanksgiving for everyone in the US.

Jesse