trade system with mob

Make a gui, in the gui put the number of input for ur trade, and 1 output for what u will recieve from the trade, after go in procedure, u go in player procedure and u choose "Open GUI for provided Player:(Ur GUI). save ur procedure, and go in ur mob procedure, put the gui procedure in the "When right click on the mob". after, u create a new procedure that u will put in the "mob update tick" after do something like this if ur GUI have 2 imput and 1 output: https://imgur.com/a/hekGSGQ . in the first slot, and the slot two, make sure to put the item that u will exchange against something, in the 2 last slot, u put what the mob will give, for me its one clock and one spell book for one time spell, (From the Magical Seed Mod)

Sorry if this is too long

Please check the forum before asking
https://mcreator.net/forum/59315/intermediate-coding-114-how-make-custom-npcs-spawn-custom-trades