function getObj(DivID) {
	return document.layers ? document.layers[DivID] : document.getElementById ?  document.getElementById(DivID) : document.all[DivID];
}

function setProperty(ObjectName, Property, Value){
	var obj = getObj(ObjectName);
	obj[Property] = Value;
}

function setDisplayImage(Image){
	setProperty("mainimage", "src", Image);
}