This sounds like a data integration job. You have a Magento site and want to supplement your existing manual process with an automated one to update key fields.
I would not write custom code for this. This is what I used to do for my clients and it is how many freelancers still do it. The problem with custom code is that it is not flexible and requires an expert to maintain it. Yet the nature of eCommerce is fluid.
The proper tool for this type of task is ETL. ETL stands for, "Extract, Transform, and Load." It is a very well established domain with mature tools. For example, it is very easy to add new inputs, clean data, verify against existing data, and perform updates. The design environment is graphical too so you don't need to be a coder.
Yesterday I built an ETL transform to take Magento ordering information and link it to DHL (shipping). My client asked for Excel macros and I showed him an ETL solution. It blew his mind :)
For this project I will deliver the following.
1. Discuss your project goals in detail.
2. Devise an ETL transform.
3. Teach you how to use and extend the solution.
4. After-project support to ensure that the solution works for you.
I am located in Alberta, Canada and have worked with clients worldwide. I am an English speaking freelancer and can bring creativity, dedication, and a wealth of experience in the computing industry to your project.
Thank you for your consideration. Please contact me to discuss my bid further.
Best regards,
Jay