First - you actually have parenthesis in a table name? Gakk! You like to make your life difficult.
Second -
Code:
SELECT TF.MyField1, TF.MyField2
FROM [Fee Billing Cur Mo (Raw Data)] AS TF
WHERE (dateadd("D",NZ(TF.[noneligible_day_cnt],NZ(TF.[TerminationDate])) > [MyDate];
should work, as long as [MyDate] is available to the SQL.
I've put NZ around the date fields to trap any null records. In general, I would do the same around the fields in June's second example, and use DateAdd rather than the + operator. But, I'm paranoid hat way.
What, precisely, do you mean when you say it returns -1? How are you doing it?