I have found something similar, except it was for cooking, but I'm sure you can use it just the same.
Here is something you could try:
=============================================
MINING.
<> Show choices: Mine ore , Leave
: Â Mine ore
<> Conditional Branch : [PickAxe] posessed
  <> Varible [001: mining] = Random 1.20
  <> Conditional Branch : Varible [001 : mining] == 1
    <> Message : you mine some gold ore.
    <> Change Items [gold ore] +1
    <>
  :   Else handler
  <> You couldnt mine anything.
  <>
  : End.
  <> Conditional Branch : Varible [001 : mining] == 2
    <> Message : you mine some copper ore.
    <> Change Items [copper ore] +1
    <>
  :   Else handler
  <> You couldnt mine anything.
  <>
  : End.
<> Conditional Branch : Varible [001 : mining] == 3
<> Message : you mine some silver ore.
<> Change Items [silver ore] +1
<>
: Else handler
<> You couldnt mine anything.
<>
: End.
*** Change and add more to ur tastes ***
====================================================
Just instead say you need 2 things to get something...
I also found this:
viewtopic.php?f=12&t=54990&hilit=cooking
Haven't tested it yet though...
And, yes, I'm still looking for the one I use...