img1on = new Image();          
        img1on.src ='images/b1b.gif';
        img1off = new Image();          
        img1off.src ='images/b1.gif';
        img2on = new Image();          
        img2on.src ='images/b2b.gif';
        img2off = new Image();          
        img2off.src ='images/b2.gif';
        img3on = new Image();
        img3on.src ='images/b3b.gif';
        img3off = new Image();          
        img3off.src ='images/b3.gif';
        img4on = new Image();          
        img4on.src ='images/b4b.gif';
        img4off = new Image();          
        img4off.src ='images/b4.gif';
                     
function imgOn(imgName) 
	{
        document[imgName].src = eval(imgName + 'on.src');
	}

function imgOff(imgName) 
	{
        document[imgName].src = eval(imgName + 'off.src');
	}