AS3 code:

var attackerDex:Number = 0; // attackers dexterity
var defenderDex:Number = 0; // defenders dexterity
var attLuckyStrike:Number = 0;// Can be 0,2 or 7
var defNinjaReflexes:Number = 0; // Can be 0 or 4
var block:Boolean = ; //Can be true or false

function block():void
{
	totalDex = attackerDex + defenderDex;
	defenderPercent = defenderDex/totalDex; //This will give a number between 0 and 1
	attackerPercent = attackerDex/totalDex; //This will give a number between 0 and 1
	blockChance =((defenderPercent + (defNinjaReflexes)) / (attackerPercent + (attLuckyStrike/100)}) * 8; 
//8 is the modifier, so if there are no cores and dexterity was equal, then: 0.5/0.5 = 1*8 thus block chance is 8%
	blockRandom = Math.Random()*100
		if blockChance < blockRandom
		{
			block = true
		}
		else
		{
			block = false
		}
}

Formula: 

Block Chance = 8% + (Defender's Dexterity - Attacker's Dexterity) / 2.5

quote:

also it still only translates to dex ratio*8% for block , meaning if you had double his dex you only get 16% block.