var btPic = new Array();

for(i=0;i<20;i++){
	btPic[i] = new Array();
	
	for(j=0;j<2;j++){
		btPic[i][j] = new Image();
		btPic[i][j].src = "images/bt_" + i + j + ".jpg";
		//alert(btPic[i][j].src)
	}
}

function tauschen(name,obj,pos){
	document.getElementById(name).src = btPic[obj][pos].src;
}