Question on developing a querie

[miner2007]

I'm trying to make a querie that shows an increase/decrease in an inventory. I want to take the total from the date previous and either add or subtract the current day's value. It would be a lot like the following in excel but trying to get in access instead. Thanks.

	5
4	9
-3	6
7	13

[JeroenMioch]

I use SQL code to achieve this. Do you have a form where the user inputs the value to add or substract ?
And are there variables like size or color, or is it just the one product's inventory that needs to be updated ?

[miner2007]

Currently there is no form for user inputs and it would be a couple product inventories with each value being different.