sorting months according to fiscal year

Hi 
I have to  rearrange the months according to the fiscal year i.e from April
to march and use the same in the order by clause of a query.
I have written the following postgresql function for the same, but to_number
is returning an error.
Can you please tell me where i'm going wrong?
Instead of the function to_number can you suggest any other function that
will convert a particular month to its corresponding month number(ex:
april=4 or jan=1)

CREATE FUNCTION sort_month(to_number('April','MM')) RETURNS numeric AS $$
DECLARE 

BEGIN
      CASE WHEN 4 THEN 1           WHEN 5 THEN 2           WHEN 6 THEN 3           WHEN 7 THEN 4           WHEN 8 THEN
5          WHEN 9 THEN 6           WHEN 10 THEN 7           WHEN 11 THEN 8           WHEN 12 THEN 9           WHEN 1
THEN10           WHEN 2 THEN 11           WHEN 3 THEN 12           ELSE 0
 
END;



$$ LANGUAGE plpgsql;



--
View this message in context:
http://postgresql.1045698.n5.nabble.com/sorting-months-according-to-fiscal-year-tp4723409p4723409.html
Sent from the PostgreSQL - sql mailing list archive at Nabble.com.