Creating a custom inventory block that acts as a shulker box

Hi, I'm trying to make a block with an inventory that acts like a shulker box. I figured out how to get the items to stay in the GUI when I exit it.I have it set so that the items don't drop from the block when I break it. But when I break the block, the items disappear. Is there a way to make the items stay in the GUI even after you break the block kind of like a shulker box?