Customising auto responder script to a membership site

We have a membership site created using PHP/MYSQL and an auto responder script (purchased from a third party and written in PHP Smarty) installed in the server. I have a need to periodically send auto responder emails to multiple member lists. The member list will be dynamically created using certain filter criteria from the membership database. The filter criteria is constant but the member list will be dynamic (as some could drop off and new members could get added). Also the email should pick up content dynamically from the member data base based on certain conditions like joining date, last login date etc. The person must integrate the autoresponder script with the member database and set up the emails to go periodically based on preset conditions. The chosen person will be expected to work with remote desktop access to view our backend programs in the membership site.