How to create a custom link from a banner ad to allow my web page to show specific information

Question

I was thinking I would like to create something on the end of a link, like:

a href="INSERT_TARGET URL_HERE"> <img src="INSERT_IMAGE_URL_HERE" alt="INSERT_ALTERNATE_TEXT_HERE" /

Where I could place a code "00000001" as the alternative text which could tell the website the origin of the redirect from my banner and the website could customize several pulldowns based on where the user emanated from.

Each banner would have its own code, that I would manually add to the link, and the site would need to read this link and act based upon the code, ie. 0000001 is from NYC, 0000002 is from Philadelphia, etc. I want to be able to prepopulate several fields based on where the user came from and I thought this could be cleaner than just asking the question, where do you live, on the webpage.

I've found discussions that use IFrame pixel, Google ads, and other third party companies like Bitly. I do not need to review the analytics, just need to customize the experience and see no need to bring on outside businesses to do, what I assume, is a simple procedure.

Thanks