Need help making shop block

I'm making a Office themed mod where you have a fax machine that when you right click it, it gives you fax paper, you can then take 9 fax paper and turn it into a stack of papers block.

here's where my issue is, I've made a block called "computer" when you right click it it brings up a GUI where you're supposed to be able to put a stack of papers block and get an item called "money'

however when I tried making this I can't use item procedure blocks (in the visual code editor) so I can't use the provided itemstack block to make it so that the correct block being placed in the slot on the computer is the stack of papers block, anybody have any ideas?