Diffrence of last 2 rows

Hi i have a table which includes meter reading of different meters. When i give the meter id i need to take the last 2 meter reading values . My table structure and datas are

CREATE TABLE MeterReading
(
 ReadingID int,
 MeterID int,
 DataCounter int,
 Value numeric(16,4)
)
INSERT INTO MeterReading 
VALUES(1, 1, 1, 102.45)
INSERT INTO MeterReading 
VALUES(2, 2, 1, 110.45)
INSERT INTO MeterReading 
VALUES(3, 1, 2, 110.58)
INSERT INTO MeterReading 
VALUES(4, 2, 2, 115.89)
INSERT INTO MeterReading 
VALUES(5, 1, 4, 120.00)
INSERT INTO MeterReading 
VALUES(6, 2, 4, 116.23)

Here i need the difference of latest (based on DataCounter) difference of Values corresponding MeterID

select top 2 * from MeterReading  
where MeterID = 1
order by DataCounter desc