Making a Field Required conditionally which is inside the template

Summary:

In Account Object we have a field for getting the Phone Number.

If we check this field in layout, It is actually a virtual field having Account Phone Template and when I check this field under Fields Tab it consist of the below highlighted fields

Now our requirement is that when user enters the Phone number without country code it should not be allowed. Once the Phone Number is entered, country code should be made required. So as I wrote the condition on Required condition of PhoneCountryCode that it should be required when RawPhoneNumber is not null.

But this doesn't seems to be working. I also tried Validation but it also didn't worked. How can we achieve this??