Can you use standard deviation to figure out the variance?
SELECT ID, STDEV(Value)
FROM
(SELECT 1 ID , 100.12 Value
UNION
SELECT 1 , 100.24
UNION
SELECT 1 , 100.35
UNION
SELECT 2 , 300.12
UNION
SELECT 2 , 100.14
UNION
SELECT 2 , 300.35
UNION
SELECT 3 , 10.12
UNION
SELECT 3 , 10.24...