Retaining selected options on html web resource

function setListOnSave()
{

		//remove all SC Option set values
		Xrm.Page.getControl("new_os1").clearOptions();

		//Get all values of First div (Software Configuration) all check box value using class name SC
		var SC = Xrm.Page.getControl("WebResource_MultipleSelect").getObject().contentWindow.document.getElementsByClassName("SC");
		var tmp=null;
		for(var i=0;i<SC.length;i++)
		{
			if(SC[i].checked)
			{
					//getting label of checked check box
					tmp+="-"+SC[i].value;

					//setting checked check box value into option set
					var opt1 = new Option();
					opt1.text = SC[i].value;
					opt1.value = 100000000+i;
					Xrm.Page.getControl('new_os1').addOption(opt1);

			}
		}




}