// 檢查 checkbox 勾選數量

var maxCheckbox = 17;
var maxSelected = 3;

function mycheck(ctrl, checkboxName) {
	var nowCtrl;
	var i = 1;
	var num = 0;
	while ((i <= maxCheckbox) && (num <= maxSelected)) {
		nowCtrl = eval("ctrl.form." + checkboxName + i);
		if ((nowCtrl.checked)) {num++;}
		i++;
	}
	if (num > maxSelected) {
		ctrl.checked = false;
		alert("最多只能選三個唷！");
	}
}