Stop the player from using an item in the secondary hand if another item is already in their hand

I have an item that works as a kind of backpack, it must be left in the secondary hand of the player to work, the problem is that other items that use the right button to attack keep opening the other item's GUI, normally this is already avoided by game as you are using a bow or something, but when both objects are ''items'' the player does the functionality of both, is there any way to prevent this from happening? because it is very annoying every time you attack with an item a GUI appears