Stock order system problem

[banburyexperience]

I am building a database for my company and I want the system to be able to return the previous value of goods in stock, i.e. the Balance field now becomes the Goods In Stock field?<br><br>For example if Goods In = 6, Quantity Sold = 2, the Balance would be 4. If I wanted to carry out the same transaction at a later date how would I make the system to return the old Balance value of 4 automatically?<br><br>Further, dealing with re-order levels, how could I make the system to alert the user when the re-orderlevel is reached on different items?<br><br>I'd appreciate any useful suggestions as I woiuld like to get a way from the present paper-based system.