Automatic Field updates when making changes to another field
I'm trying to create an inventory of products. I want to enter a qty for each item, and then find out the balance of that particular item after I purchase more of it, or subtract from it. The balance should reflect all purchases and sales of that particular item.I believe my fields will be something like this...
Qty Used (this field will be updated many times)
Qty Purchased (this field will be updated many times)
Running Balance (this field should reflect the Qty used and Qty Purchased for a Specific Product, no matter how many times the fields have been altered)
I will also have a field of dates to reflect when the purchase was made or when the product was used.
Does anyone know a simple way to do this?