Is it possible to force unique values on the same form before it can be submitted?

For example: I have a form with two number fields. These fields can not be the same value. I've put it in the "Instructions" but it is often ignored and the form is being submitted with the same value in both fields. I've tried to check the no duplicates, but that apparently only checks that field in all of the existing records. I need it to check all fields on the same form.