Formula Error For Inventory Sheet

ShaunJM 

I am wanting to keep track of a small group of stock items, and would like the following to happen :

( cells named for ease )

Cell B5 - Total Quantity of item in location A ( needs to be able to be manually increased as stock comes in )

Cell C5 - Quantity of said item in a location B

Cell D5 - Quantity of said item in location C

When items are taken from location A and placed in either location B or C ( which i manually change the quantity in the cell ), i would like the total in cell B5 to automatically lower whilst being able to manually increase B5 when stock replacement arrives. It works untill i manually increase B5, as this then clears my formula.

If I can be so bold, I'd encourage you to re-think your design, altogether. A major part of keeping track of items in an inventory is having a clear history of what has happened with those items in inventory. And what you've described does not keep history.  This is clear from the several uses of "manually change/increase" in that quoted paragraph.

I've attached a very simple--and I do mean both words; it could be developed with far more details and nuance--example of how a record of history could be created, and still give you an ongoing current count. And note, the history can enable you to go back at any time and discover what has led to the current levels.