By valid, do you mean that the fields have something in them verses they are empty? Remember that invalid fields can be things like an invalid date or something that does not pass the validation requirement for a field. It appears you are only looking for empty fields.
If you want, you can use the FieldNames function to set a variable that has a list of all the fields in your table and, with that array, then have a loop that goes through and tests each field for whether it is empty or not. That is what I would do.