Making an item usable on event

[Someone]

Basically I'm trying to figure out how to make an item usable only on an event. 

1. You interact with the event and item window opens for you to choose which item you'd like to use. (I've done this part.)
2. You use the special item which triggers another event.

However, when it opens the item window I can't use the item because I have it set to Occasion: Never because don't want the player to be able to use the item other than on the event.

Seems you try to use the system of Level 5 games like Dark Cloud and Rogue Galaxy.

I just got an idea, did you set it as key item?
I think you have to use the Item via an event conditional branch.
If x Item is in your Inventory, a choose option will pop up.  
Or maybe make a call common event for all those selectable Items to choose from or something like that.

Here is another Idea:
Set a variable or a switch for the selectable event, If off the Item can not be used, If on the item can be used.
It could be activated at selecting the item or a tile before it via player touch or through a common event for those specific items.
I don't know if it will work out but it worth a try i guess.