function setBlueTreeArrow(arrowImg) {
	setTreeArrow(arrowImg, "arrow_blue.gif");
}
function setGrayTreeArrow(arrowImg) {
	setTreeArrow(arrowImg, "arrow_gray.gif");
}

function setTreeArrow(arrowImg, arrowName) {
	arrowImg.src = "tree/"+ arrowName;
}