function switchImage(page_no, c, b) {
	
var path="";
if(page_no < 10){
	path="dl.php?bn="+ c +"&book=" + b + "&file=page00";
}
else if(page_no<100 && page_no > 9){
	path="dl.php?bn="+ c +"&book=" + b + "&file=page0";
}
else{
	path="dl.php?bn="+ c +"&book=" + b + "&file=page";
}
document.form2.page_no.value=page_no;
document.prod_img.src=path + page_no + ".jpg";
}

function next_img(a,b){
	var i="";
	i=document.form2.page_no.value;
	var numValue = (+i);
	numValue=numValue+1;
	switchImage(numValue, a,b);
}

function previous_img(a,b){
var i="";
i=document.form2.page_no.value;
var numValue = (+i);
numValue=numValue-1;
switchImage(numValue,a,b);
}