Alter PHP database posting script and search script

This is a classified script. I will have roughly 400 cities. Each category has it's own table. The script is already written to pull the information from the database and display it as I want. However, I need the script altered so it only pulls the information for each individual city. For instance, under Chicago I only want the ads for "Jobs Available - Sales" in Chicago to be pulled from the database and displayed. i will need my search script altered to do almost the same thing. I do not want anyone who will try to redesign my site. I just want someone to make these alterations to the existing script.