HealthStone Watcher Mod (need help with traded items)

[SonicUK]

This is my first attempt at a proper mod atm i have a pretty grey healthstone icon which appears next to each party member if the player is a warlock. While i'm making it i set it so i can just click the icon to change it to a lit up health stone. I've managed to get the healthstone to return to grey when the party member uses thier healthstone, but i need help making it light up on its own :P so what i need is:

- when there is a trade, who it was to, and if a healthstone of any rank was traded.

then i can check if that player is in the party and light up icons accordingly.

[SonicUK]

I had a brief look at this for my self. i think i can pick out if theres a healthstone and who it was too, but which events do i need to watch for a successful & failed trade? (not sure if i'll need failed)