Crafting output overwrites item instead of adding it to the stack.

I've been making an own crafting block. Everything is working basically, but if you craft an item thats stackable, it overwrites the item thats already in the output slot instead of adding it to the stack. There is a procedure block which i THOUGHT was the solution, but the dependencies won't work with the GUIButton i use for triggering the Craftingprocedure, any idea how to fix this? (And can somebody PLEASE tell me how to add images to Forum entries? Everytime i try, they won't load)