Any way to change a people picker field to "No Blank" depending on result of radio button or drop down list selection?

Hi, 

I have 3 people pickers on a form that I would like to make required or not required depending on what users choose from either Radio buttons or form a dropdown list.  I can't just make these 3 fields all required prior to users submitting the form because it really depends on what users is requesting.

Thank you.