Add a custom field in the product administration

[ludojlm]

Hello,

Our website needs to be able to add a specific reference for products and clients.

Exemple : We have a product AA001, company A and company B. Company A has the product in their catalog registered under PR0025, so our reference means nothing for them.

We want to be able to add the field in the administration page where we can select the group of customer (the company) and save the new reference, so it appears like that when they're connected : AA001 - PR0025. 

So I just need to know where to change the files for adding this field. The selection of the group will be in AJAX and be handled asynchronously.

Thanks for you help!