Jason - IF AVG([GPA]) >= 1 and AVG([GPA]) <= 4 then AVG([GPA]) ELSE NULL END
Should work fine. Let me know if it doesn't.
Thank you for the help. The formula you gave me didn't want to filter out the zeros, but it lead me to the correct logic. I changed the field to this:
IF [GPA] > 0 AND([GPA]<= 4 THEN [GPA] ELSE NULL END
Then I drug the pill into the worksheet and set the aggregation calculation for AVG. Presto! All fixed now.