Multifield/range validation 2: highlighting fields

Hi,

I've just opened a question on SO:
http://stackoverflow.com/questions/12448239/multifield-range-validation-2-highlighting-fields

Shortly: using :base in self.errors.add rise up 1 error but no fields
results "highlighted", and I need that, just like using attributes
symbols in errors.add

How could I do it? It's possible?

many thanks for the help,

enrico