PHP script to edit database of vBulletin 5

I'm looking for someone to write me a PHP script which is able to write to a specific field in the USER database of vBulletin 5 without any additional MYSQL login information. The script should use the existing vBulletin functions. The script must be fully commented! It can either be a standalone script which I'll call or a small piece of code I'll add into my existing script (which is what I prefer though). Don't forget to tell me how long you'll need for this in case you're interested. Everything goes via freelancer only!