I want to make an Item that heals the user(Elixir, vulnerary), but after you use it, it poisons you. Is that possible?
See my asm thread - item special effect.
Also see the use vulnerary asmc that Stanh wrote, which can be found in the pokemblem buildfile github.
Assuming that’s not quite enough to go on, let me know that this half solution works for you and I’ll try to put together an example installer for you sometime.