Create a custom tab on Customer Detail

Hello.

We need to have the option to limit quantities by product on the web site;
Each customer will have a different quota for each product.
Example:
Customer A1 & Product B1 -> quota = 10
Customer A1 & Product B2 -> quota = 20
Customer A2 & Product B1 -> quota = 200
Customer A2 & Product B2 -> quota = no limit
.....
My idea is to create a custom tab in customer detail and display data related to product and quota.

Thanks.