General :: Table Structure For Multi Location Warehouse

I am working with Access 2007. I have a pretty good working knowledge of access. Here is my problem. I have a warehouse which supports four departments. The warehouse floor area is segragated into four areas. Area 1 department 1, area 2 department 2, and so on. Each department uses the same commodity, so I will have four of each item, belonging to each department. The storage locations will be unique and not repeated anywhere in any department. I receive and issue items for all departments.

The problem is how do I structure the tables and queries to receive an item for department 1 adding it to department 1 only and not have the item added to another department with the same item. Also to issue the item from a department 1 without effecting the on hand balance of any other department. I am too the point of creating 4 separate databases one for each department.