Let's assume that you have some test data in a table named [NSE20] that looks like this
Dates PXLast
---------- ------
2010-07-01 131
2010-12-31 130
2011-11-12 123
2011-12-30 125
2012-01-03 127
2012-12-31 129
I'd start by creating a saved query in Access named [NSE20_year_ends] that identifies the year-end dates by (calendar) year:
SELECT Year(Dates) AS CalendarYear, Max(Dates) AS YearEndDate
FROM NSE20
GROUP BY Year(Dates)
That will produce
CalendarYear YearEndDate
------------ -----------
2010 2010-12-31
2011 2011-12-30
2012 2012-12-31
Then I'd create another saved query named [NSE20_year_end_balances] to extract the closing balances for each year:
SELECT NSE20_year_ends.CalendarYear, NSE20.PXLast
FROM
NSE20
INNER JOIN
NSE20_year_ends
ON NSE20.Dates = NSE20_year_ends.YearEndDate
That will give us
CalendarYear PXLast
------------ ------
2010 130
2011 125
2012 129
Now we can do a self-join on that query to calculate the percentage change
SELECT
y1.CalendarYear,
(y1.PXLast - y0.PXLast) / y0.PXLast * 100 AS PctChange
FROM
NSE20_year_end_balances y1
INNER JOIN
NSE20_year_end_balances y0
ON y0.CalendarYear = y1.CalendarYear - 1
resulting in
CalendarYear PctChange
------------ -----------------
2011 -3.84615384615385
2012 3.2