How to know from wich slot an item has been taken

Hi

I started with MCreator and enjoy the tool a lot. For most situations I could find a solution by trying or searching the web. Now I am facing an issue I don't see any solution:

I have a GUI with 2 input blocks. Below I have 9 output slots. Now when I insert sticks in slot 0 and wooden planks in slot 1 my procedure is checking if there is enough. If so it will put possible crafts in the 9 output slots.

In this example it will put a hoe, axe, hatchet and shovel in the first 4 output blocks.

The goal: When i take one of these items from the output slots I want it to remove the according amount of items from slots 0 and 1. When taking the hoe it should remove 1 plank while taking pickaxe should remove 3 (beside removing 2 sticks of course, but thats the same for all). 

My problem: How can I know wich item is taken? Either knowing the item or the according slot would help but I couldn't find a way for both.

Looping through the slots won't help me I guess since I can check what IS in the slot but not what was there before.

I found no similar question in forum - if I just overlooked please excuse me.

Thanks for any ideas and help

Domi