scheduling stored procedure

Hi,

I have a temporary table in which i store all emails of users who want to receive a newsletter.
to avoid spamming and to limit the size of this table, i would like to delete all requests (records) which are older than 72 hours.

i was thinking to execute each hour a stored procedure which will check the time and date (of now) if it is greater than "registration request time" stored in this temporary table.
if it is greater, so record will be deleted.

does postgresql have such timer (something like "cron" under unix/linux) ?

thanks a lot,

--
Alain
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Windows XP SP2
PostgreSQL 8.2.4 / MS SQL server 2005
Apache 2.2.4
PHP 5.2.4
C# 2005-2008