// sum the values of the string "a" e.g. 3,2,4,1 = 10
function GetSum(a) {
	// split the passed string into new array
	var nums = a.split(',');
	var total = 0;
	// loop and build total, converting strings to numbers on-the-fly
	for(var i = 0; i < nums.length; i++) total += Number(nums[i]);
	return total;
}