Inventory reductions/additions via spreadsheet

[Michael_Buglio]

I would like to be able to upload a CSV to take inventory out of our system

ie I have 20 widgets in inventory

I sold 5 widgets off site without logging them in Shopify

I want to upload a file that says Widgets inventory -5 

the inventory page in the main part of Shopify seems to just replace the inventory number.  So if I import an inventory file with -5, it changes my inventory from 20 to -5

Any thoughts or suggestions welcome