b1  = new Image();
b1.src="img/pfeil_hover.gif";
bn1= new Image();
bn1.src="img/pfeil.gif";

bback_hover  = new Image();
bback_hover.src="img/pfeil_hover_back.gif";
bback= new Image();
bback.src="img/pfeil_back.gif";

function bw(Bildnr,Bildobjekt)
{
window.document.images[Bildnr].src=Bildobjekt.src;
}