We cannot tell you how to write a program like that line by line. Its impractical. If you're new to programming, don't just jump into developing CRUD applications just like that. Spend some time with a couple of good books/tutorials and get a firm hold of the basics. And if you're writing a stock control system, there will be a backend database where you store the data. You'll need to learn SQL upto some extent. (how to create tables, set relationships between them, writing SPs, Functions etc) I suggest you choose Microsoft SQL Server 2008 as the database server. You can download a free version of it from
here.
Spend some time learning and you'll find it easier to develop a simple CRUD application like that. If you get stuck somewhere, post that exact problem here with the code you have written for that. Then we can help you with that.
Good Luck!