Clear Checkboxes when form closes

I'm diligently trying to relearn Access after a 10 year hiatus. So you may see me a lot. ;)

I have an attendance form that is filled out weekly that will update in my table for with correct date. I have 2 details that I would like to solve. The first is that when I check off who was in attendance and update my table, I am unable to clear the checkboxes so that I can start from scratch with my attendance. I would like a button to clear them.

The other issue I am having is my Refresh/RunQuery button in the same form. I use this button to update my table. The problem is that when if I push the button before I'm done, I will have duplicates for every time I push the button. I have set up a Look for duplicate Records query, but I am wondering if this is the easiest way.

Thanks. Caryn