If you absolutely must define your own language, I suggest reading up on parsing: http://en.wikipedia.org/wiki/Parsing
Then, you can make your own pseudo-language that is simply used for your game and therefore easily usable:
Filename: ChainLightning.spell "Chain Lightning" required $caster $power $cost decrease MANA of $caster by $cost select $a in range(4,$caster) select $b in range(1,$a) select $c in range(1,$b) damage $a by $power damage $b by [$power/2] damage $c by [$power/4]
This type of language is easily parsable and readable by the average non-programmer. The disadvantage is the strictness of the syntax and lack of power, obviously.