var sendForm = false;

function prepareSubmit(form) {
	if(!sendForm) validateComparisonLink(form);
	return sendForm;
}

function validateComparisonLink(form) {
	sendForm = true;
 	if(comparisonLinkCount(form) == 0) {
 		alert("Please select at least one product");
		sendForm = false;
 	} 

 	if(comparisonLinkCount(form) > 10) {
 		alert("Please select up to 10 products only");
 		sendForm = false;
 	} 
}

function comparisonLinkCount(form) {
	var numLinks = 0;
	var fieldName = "";
	var fieldtype = "";
	
	for(i=0;i<form.elements.length;i++) {
		fieldName = form.elements[i].name;
		fieldType = form.elements[i].type;
		if(fieldType=="checkbox" && fieldName.toLowerCase().indexOf("compids")!=-1) {
			if(form.elements[i].checked) numLinks++;
		}
	}
	
	return numLinks;
}