Column aliases in having or where for Postgres 8.3

Hi,

Anyone knows if I can use column aliases in having condition?
Something like this.

pgdb=# select sum(c_acctbal) as p from customer having p >
1000;

select sum(c_acctbal) as p from customer having p >
1000;

ERROR: column "p" does not
exist

LINE 1: select sum(c_acctbal) as p from customer having p >
1000;

^

--
Best Regards,
Prafulla V Tekawade