Counter adding multiple clicks of hotspots

Hello, 

I created a scene on a slide with multiple hotspots laid over an image. The instructions tell the user there are 6 spots they are looking for so I created a counter to help them keep track. I want each hotspot to count only once so the number doesn't go over 6. 

I set up the counter to stop counting at 6, but I cant figure out how to disable counting the same hotspot more than once. Does anyone know how to do that?

Thank you!

Alex