Add cells in a table

[Demetious]

I have an inventory table. I have a form to look at the data. I want to give the user the ability to add more of any particular inventory in the "In Stock" Field of the inventory table. I realize that "In Stock" needs to be made up of two other fields which are in a table named transactions and the two fields are "Old Quantity" and "Transaction Quantity".How do I do this? Later I will need to be able to remove/shrink as well but once I have this basic concept, I think I can manage the rest. Thanks

 

[HiTechCoach]

You should always create a transaction record to make any changes to the stock level.