Can't use item unless another is present

I'm going to assume that this would require a script, so here I am.

In my game you don't use skills to attack, you scavenge for items. One of the items is a slingshot, and then you find the ammo elsewhere. Is it possible to make it so that the ammo item cannot be used unless the slingshot is in the inventory?

(P.S. I've tried figuring it out with common events, but doing that wouldn't allow the player to direct the attack at which enemy they want, and would also not follow a damage formula but instead just a set HP decrease.)

I've moved this thread to Script Requests. Thank you.

Bump?

In battle? In the menu? or in general item use?

In general item use.

Hm, this is what I assume:

You have an aiming skill with a Common Event feature.
You have another skill that deals damage.

The Common Event uses Force Action that chooses the Last Target for the damage-dealing skill. As your aiming skill "attacks" first, it will then execute the damage skill at your selected target.

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As for the common event, I suppose I should first make the ammo non-consumable. Then I would write the event like this:

If Item [Slingshot] in Inventory
-Force Action [Slingshot Shoot] (Last Target)
-Change Item [Pebble]: Decrease by 1
else
-Message: Got nothing to Shoot With.
end