function buttonOn (imgName, triName) {
	if(document.images)  {
		buttonover = eval(imgName + "_on.src");
                triover = tri_on.src;
		document[imgName].src = buttonover;
                document[triName].src = triover;
	}
}

function buttonOff (imgName, triName) {
	if(document.images) {
		buttonnormal = eval(imgName + "_off.src");
                trinormal = tri_off.src;
		document[imgName].src = buttonnormal;
                document[triName].src = trinormal;
	}
}