on inventory click:

@if name of player's current inventory is "이름":

@@if name of clicked item is "이름":

@@@대충 조건:

@@@@[구문]

https://github.com/APickledWalrus/skript-gui/wiki/2.-Modifying-the-contents-of-a-GUI 참고 하셔서, 

command /opengui:
  trigger:
    create a gui with virtual chest inventory with 3 rows named "My EPIC GUI!" and shape "xxxxxxxxx", "x-------x", and "xxxxxxxxx":
      make gui slot "x" with dirt named "! BORDER !":
        send "Say goodbye to your GUI border %player%!" to player
        remove gui slot "x"
    open the last gui for the player

꼴이 되게 만들어보세요.