Chiselesc mod, not working properly

I am trying to make a chiselesc part of my mod, and am attempting to use an item/block to chisel the blocks.

It works by when the gui is changed setting the other slots to have the same number of items.  however they dont change until the next time I change the slot.

I.e. if I put 64 blocks into the input slot, the output slot doesnt change to 64 until I change the input slot again.  and then because the output slot has 64 in it, it sets the input back to 64, even though I might of just taken 32 out of it.