Ups, so ist's richtig:

[Thomas J.]

function changeImage(layer,imgName,imgObj) {
if (document.layers)
eval('document.'+layer+'.document.images["'+imgName+'"].src = '+imgObj+'.src')
else document.images[imgName].src = eval(imgObj+".src")}

Wobei:
layer = <div id="layer" ...
imgName = <img name="name" src=" ...
imgObj = obj = new Image();
      obj.src = "...

Guten Tag übrigens, soviel Zeit muß sein.