I have no idea how to do it, but you could do like this: in the treasure chest's action link, make the engine do this:
Change globals: gb_luck random &&Luck;
Change globals(2): gb_chanceglobal random 100 (or 50, or 10, depending on how high your statistics are)
Conditional: if gb_luck is greater then gb_changeglobal do: drop some nice thing else do: random item drop
You could make this system better if you want more kinds of treasure 
Good luck...
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