Can I add in logic so if radio button "No" is selected, then make the "Comments" text field *Required?

So I have a form with radio buttons Yes and No.  What I want to achieve is:

When Yes is selected the Comments text field is not required; but

When No is selected the Comments text field required, so as to force them to answer why they chose No.

Is this possible? 

I do not know code or Javascript so please explain as if I'm a 5 yr old.

Many thanks in advance

AJ