AJAX JQUERY Auto Refresh Script Based on Results.

I have a script which needs to run around 70,000ish records held in my database, however its too many to run in one process, so instead it runs around 250-500 records at a time which is more manageable, this then creates the issue of the script needing to be run several times until all the records have been processed. At first i was using an iFrame which called my php script using the auto refresh command. however depending on the records, sometimes it might take 2mins to complete 500 records or 20mins so a fixed timer is out of the question as it means the time required to process all the records takes much longer. So my thinking was to use something like aJax and/or jQuery to keep executing my php script file. But its important that its only executed again when ready. The script does print/echo information which i would like to see if possible, so i can see it working. But i could also output custom text when the script has completed like <? ECHO "FINSIHED"; ?> this could be used by AJAX and jQuery to know when it needs to execute my php script again? This project must be done in php, ajax, jquery due to my own programming knowledge limited to PHP etc. My experience in AJAX and jQuery is none existent hence me posting this job. I would like someone who really understands this project and therefore require everyone interested and bidding on this project to send me a message, with the title CHRISTMAS, so i know you've taken the time to read the above project, i would also like some who might be able to add extras to the above if required later on, or during the project. Someone who can also give a basic demo to help me choose the right person would also help.