Automatically select an option from a drop-down based on value of other cell?

I have a row where if you write "no" into the first cell, the others return "n/a" if they aren't relevant using =IF(A2="No","N/A",""). However, one of the columns is a drop-down list with "yes","no", and "n/a". I would like the "n/a" option to automatically select so that n/a appears if "no" is written into A2. I tried making a formula one of the options in the drop-down but it didn't work. Just to claridy, I need the drop-down cell (say, B2) to remain blank when anything other than "no" is in cell A2, but return "n/a" when "no" is in A2, and still be able to select other options from the drop-down in B2. Thanks for your time!