Item condition combination

OK, I'm sure some of you will understand what I mean when I say this. I want a trigger that, when the hero is holding a certain 3 items, it will take the items and continue.

Imagine a system like in Risk where each item has a classification like Infantry, Cavalry, or Artillery. That's how I want it.

I came up with 2 possible meathods.

The first will most likely work, but is long and drawn out. I make a trigger that detects if the first slot is a certain item, store a variable for type 1 2 or 3, then do number 2, then 3, then 4, then 5, then 6. Unfortunately I have many items, and this would be a very annoying bulky script.

The second is more reasonable, but I don't know how to go about it. Because the player should be able to choose which items he wants combined, he should be able to activate the item, which would store that as ingredient 1, then the next would be ingredient 2. If he uses the Exit ability, the items are returned to him(so he can't use the same item twice)

What variable can I use to measure which item was just used?(do I have to have each item cast a different base spell?! I have over 40 items, and this would be almost impossible to use dummies)

O m g. You'd be surprised how often somebody looks over what they need. i just saw the Event- Unit uses an item.

Still... I'll try to make this script, and if you guys want to know how to do it too, then I'll tell you to the best of my abilities.