Excel formula

Hi Superstars, please help, I just cannot wrap my head around this function I'm trying to do.

I have a spreadsheet of my daughter's medication, I have counted out the number of pills she has "in stock", how much she needs to take on a daily basis and how many days stock she has. I would like excel to automatically calculate how the amounts remaining once we plug in a yes/no in a cell. Sheet attached for you to see what I am talking about (I am shocking at communication)

Thank you

Dorothy