function changeSharePriceGraphPeriod() 
{
	var oDiv = document.getElementById("sharepricegraph");
	var oPeriodList = document.getElementById("sharepricegraphperiod");
	var sImageSource = oDiv.getAttribute("imagebase");
	var sURL = sImageSource + oPeriodList.options[oPeriodList.selectedIndex].value;
	oDiv.style.background = "url(" + sURL + ")";
}