22099 controlled email release

we need a simple script which can be installed on 2 of our sites, there both shared hosting with the same host so its not a dedicated server, 1 site is similar to scriptlance and has the facility to mass email all members, the other site we use to send html emails to our customer base. The script we need must be able to control the email flow rate so that only 1 email is released every 2 seconds. Our server is a Linux Server,PHP Version 4.3.11, most standard scripts installed. thanks