It seems the best way to do this is make a item switch (you can do this for multiple items with the same switch) called Item_Used or something, and have various items turn it on. Then you can have some sort of thing where if it's the right item, you make a condition for the first switch (see parameter 3), and if not inside the second switch (see parameter 4) make a more or less empty switch, except to turn stuff off.
Doing it this way, you can also have multiple switches, and check for other items (you can't seem to have the same switch, running this process twice though).
Apparently, I must've cut this for size. To run the demo, use the RTP to put stuff back in.