Im not going to answer directly, but I am going to help you.
When presented with a problem, you need to stand back, and look at what method you are going to take.
Look at how it could possibly be achieved, and what could be needed in order to do it.
In your case, there are several options. Sketch them all out, ON PAPER, and see which one is more feasable.
Success is ALWAYS in the planning. If you don't know HOW you are going to achieve your goal, you are no-where near it.
As for your problem, you could, along with your user records in your database (or other storage of user records, if you arent using a database) also put a user url, that way you can access that property, and set them individually...