I'm helping to make a minigame where the player needs to sort items into the correct color shulker box. It uses redstone to detect if you put the wrong item into a shulker box, but I'm trying to make a command block system that will activate if the number of items in your inventory exceeds a maximum amount. I'm pretty sure this is done with either the execute command or the scoreboard command (or both), but I don't have the command knowledge to figure it out. Can anyone offer assistance?

P.S. Sorry if this is the wrong place for this. I don't post in the forums often/at all, so I really am not sure where to put this.