descriptive flexfield - set attribute2 as mandatory if attribute1 = YES, possible?

HI : Is this possible? if yes, how?  if not, what other option do I have?

We have a simple DDF that already defined for Vendor site that allow user to entry exchange rate

    Name : Yearly Currency Rate on       attribute1       YES or No

    Name  : Currency Rate                      attribute2        1.2%

    name   : Expirataion date                   attribute3         10-DEC-2017

The new requirement is that if the "Yearly Currency Rate on" ( attribute1 ) is change to YES ( from NULL or NO )

the Currency Rate ( attribute 2 ) and Expiration date ( attribute3 ) must be mandatory.

I take a quick research and I don't see that is possible in DDF setup.  ( or I just did not know the right way ).  I also found that you cannot apply this rule through form personalization since that is DDF.  .. n