//load images into array
imgList = new Array (
							'mhd_pnav01',
							'mhd_pnav02',
							'mhd_pnav03',
							'mhd_pnav04',
							'mhd_pnav05',
							'mhd_pnav06'
						);

for (i=0; i<imgList.length; i++) {
		eval(imgList[i] + "_off = new Image; " + imgList[i] + 
"_off.src = 'imgs/" + imgList[i] +"_off.gif';");
		eval(imgList[i] + "_on = new Image; " + imgList[i] + 
"_on.src = 'imgs/" + imgList[i] +"_on.gif';");
	}

function unroll(img) {
		eval("document.images['"+img+"'].src = "+img+"_off.src;");
	}

function roll(img) {
		eval("document.images['"+img+"'].src ="+img+"_on.src;");
	}