Inventory changed to chat

I have an object being used for a contest. To enter, you'll drop a no copy notecard. When the box is touched, it gives a random inventory item.
What I would LIKE to do is...
if John Doe drops their item in..
Contest Box: John Doe has entered the contest!

you can not detect who dropped an item.

You could make them "touch" the box, which would start a (15 second? 30 second?) timer.. and allow them to drop an item while the box was green. Then anyone could drop an item while the box was green, and the person who touched it would get credit. You could add a sensor (say 5m).. and seach for the toucher.. and if they left range, the box could go back into "no drop" mode.

I have seen many things that detect changed inventory. How is that done, precisely?

with the changed event

     changed (integer change)
     {
          if (change & CHANGED_INVENTORY)
          {
               //do stuff
          }
     }

You can detect THAT the inventory HAS changed.. and through some detective work, you can even determine which item is "new" or whether an item was added or removed (by comparing it to a list or count of items from before the drop)... You can also determine who created the new item, but you can't actually discern who dropped it in.

You... ROCK.
Thank you!