Calculating Stock

We are a high end jewellery business and I am about to start a project to cover the entire business.  The first part of this project will be calculating stock in multiple branches.  I will need to be able to calculate the stock values and quantities for different dates at all times, so for instance today is 31st January 2017, how do my stock levels compare to 31st January 2016.

Most stock is made up of one off pieces although some repeating products might have 20 years of history and up to 100 sales.  There would generally be up to 15,000 different articles in stock at any one time, but I feel I should be thinking about growth in this area.

I know that I am asking a huge question for a forum, instead I am asking where should I look for answers to this?

At the moment I imagine a movements table, that will have the fields, 

Date of movement

Entry Qty

Sale Qty

Sale Return Qty

Exit Qty 

Correction Qty (this is for when things don't give us the correct answer)