Creating a function

Hi,

I am trying to create a function to bin based on user value and I am
stuck. I followed the
postgres create function tutoriall but I am missing something. Any help
would be appreciated as I think I am just going further off course at this
point

Glenn

CREATE FUNCTION "IncentiveBin"(in Gwac double precision,
in MtgRaate double precision,
in BinSize double precision)
RETURNS double precision
LANGUAGE 'sql'
VOLATILE PARALLEL SAFE
AS
$function$
BEGIN
ceiling((Gwac - MtgRate)/BinSize) * BinSize;
END
$function$