function return update count

Hello:

I am try to get a function to return the count of the rows updated within
the function.
As in the following, I wan the number of rows updated to be returned.

This is a simple update, other update statements that I need to write will
be complicated.

CREATE OR REPLACE FUNCTION est_idio_return_stats_update()
RETURNS integer AS

'
update est_idiosyncratic_return_stats set delta_avg_60 = avg_60 -
period_61_return, delta_avg_last_24 = avg_last_24 - period_61_return,
delta_avg_last_18 = avg_last_18 - period_61_return,
delta_avg_last_12 = avg_last_12 - period_61_return,
delta_avg_last_6 = avg_last_06 - period_61_return ;
'

LANGUAGE SQL ;

The above returns the following:
ERROR: return type mismatch in function declared to return integer
DETAIL: Function's final statement must be SELECT or INSERT/UPDATE/DELETE
RETURNING.
CONTEXT: SQL function "est_idio_return_stats_update"

********** Error **********

ERROR: return type mismatch in function declared to return integer
SQL state: 42P13
Detail: Function's final statement must be SELECT or INSERT/UPDATE/DELETE
RETURNING.
Context: SQL function "est_idio_return_stats_update"

Thanks for your kind assistance.

KD