Cycle counts from linked sheets: everchanging quantities

Hey everyone, this is my first time here, I just had a question in my mind and wanted to know if such a thing was possible or nonsensical:

The industry I work in, we use Excel to keep track of cycle counts we do on our inventory on hand from time to time. When one of our guys gives us a quantity, we enter that quantity into one cell while an adjacent cell holds the original quantity on hand to compare it to.

For the time being, almost all the data is static and manually entered from various sources, but mainly from our company ERP software.

What I want to do is this: I want to pull the quantity on hand for a specific item from another Excel file that dynamically updates itself on that parameter.

So, in essence, each time the sheet opens up, the quantity on hand would change: one day the item can have 100 pieces, the next day it can drop to 90 pieces if 10 pieces were picked. But in the interim, I had cycle counted 95 pieces.

Now since there was a drop of 10 pieces, I would have to drop the cycle count figure accordingly to 85 pieces from the original 95.

Question is: is there a way for Excel to recognize the drop in quantity on hand during each update, and then apply that difference to other cells as well?

Please let me know if you need more information, thanks.

I really like the link... I have found here so many information, I'll share this to my friends...



........................
Aries86