Inventory log: Add or Subtract values from another sheet

I need help, attached is a simplified copy of what i'm trying to do. I already have a spreadsheet that does all this but based on how many different classes and subclasses I have it became a workbook with multiple sheets. I'm trying to simplify it and break it down to 2 sheets, problem is Im sure i'll need to use VBA which im not good at. Any helpers?

I have a starting available value, I need to add or subtract from that value based selecting "consumed" or "purchased" on a different sheet. I need the formula to continue going consistently as I continue adding to my log.

For example:

If I have 100 of [Class] Soap, [Subclass] A
I "Consumed" 50
My new "Available Value" = 50

on the next day I add to my log that I "purchased" 50 of [Class] Soap, [Subclass] A
My new "Available Value" = 100

There are multiple [Classes] and [Subclasses]

Let me know if you need more clarification! Thanks in advanced!

Each subclass would have its own inventory amount. So, if the clothes class were all the same sub class then the answer would be depending on whether we "purchased" or "consumed".

For example:

Starting inventory for Clothes [subclass] E = 100

I enter in my log:
Row1= [Clothes], [E], [Consumed] "10"

Row2= [Clothes], [E], [Consumed] "10"

Row3= [Clothes], [E], [Consumed] "10"

Then the answer would be 70, if they were [Purchased] the answer would be 130

Hey guys I was on a time crunch at work, so I ended up taking what I had originally and just adding some toggle buttons to hide/unhide the columns. Thanks for the help! I spread the love!