Fishing Net Help

I want to create a Fishing net that has its own GUI.  How it works is when placed in water and add bait into the fishing net it will slowly catch fish.  depending on the bait you put in you have a chance of catching other things like enchantment books and goodies.  What i cant seem to figure out is how to make the Fishing net actually slowly take the bait and give the fish.  Any ideas?