Help with SQL statement in query

Others have contributed a SQL statement from another newsgroup (see below).
The only remaining issue is to add something to the expression so that it
also displays the results of a sum of all [RESULT] values that have a "null"
value in the [QUAL] field and not only compare them to those with "not null"
values. Please see the ongoing thread here
http://www.microsoft.com/communities...968&sloc=en-us

SQL Statement:

SELECT X1.LAB_ID, 'max_of' AS aggregate_type,
MAX(IIF(X1.QUAL IS NULL, NULL, X1.[RESULT])) AS aggregate_value
FROM Xylenes AS X1
WHERE NOT EXISTS (
SELECT *
FROM Xylenes AS X2
WHERE X2.LAB_ID = X1.LAB_ID
AND X2.QUAL IS NULL
)
GROUP BY X1.LAB_ID
UNION ALL SELECT X1.LAB_ID, 'sum_of',
SUM(IIF(X1.QUAL IS NOT NULL, NOT NULL, X1.[RESULT]))
FROM Xylenes AS X1
WHERE EXISTS (
SELECT *
FROM Xylenes AS X2
WHERE X2.LAB_ID = X1.LAB_ID
AND X2.QUAL IS NOT NULL
)
GROUP BY X1.LAB_ID
ORDER BY 1;
--
Barry Guidry