Skill validation

function Checkskill(sender, args)
{
BaseContrl = document.getElementById('<%= this.GridView1.ClientID %>');
var ChildContro = "CheckBoxList2";
var Inputs1 = BaseContrl.getElementsByTagName("input");
var ischecked=false;
args.IsValid =false;
for(i=0;i<Inputs1.length;i++)
{
var opt = Inputs1[i];
if(opt.type=="checkbox" && opt.id.indexOf(ChildContro, 0) >= 0 && opt.checked)
{
if(opt.checked)
{
    ischecked= true;
    args.IsValid = true;                
}
}
}

}