function GetNumChecked()
{
	var num_checked = 0;
	var check_form = document.getElementById('checks');
	var objCheckBoxes = check_form.elements.songs;
	var countCheckBoxes = objCheckBoxes.length;

	for(var i = 0; i < countCheckBoxes; i++)
	{
		if (objCheckBoxes[i].checked == true)
		{
			num_checked = num_checked+1;
		}
	}
	return num_checked;
}

function UpdateDonateBox(obj)
{
	var num_checked = GetNumChecked();
	var donate_form = document.getElementById('donate');
	donate_form.elements.amount.value = num_checked;
}

function UpdatePaypalForm()
{
	var check_form = document.getElementById('checks');
	var objCheckBoxes = check_form.elements.songs;
	var countCheckBoxes = objCheckBoxes.length;
	
	var index = 0;
	var song_ids = new Array();

	for(var i = 0; i < countCheckBoxes; i++)
	{
		if (objCheckBoxes[i].checked == true)
		{
			song_ids[index] = objCheckBoxes[i].id.substring(5);
			index = index + 1;
		}
	}

	var donate_form = document.getElementById('donate');
	var item_number = song_ids.join(':');
	
	donate_form.elements.item_number.value = item_number;
}

function minDon()
{
	var num_checked   = GetNumChecked();
	var donate_form   = document.getElementById('donate');
	var donate_amount = donate_form.elements.amount.value;
	if (donate_amount < num_checked)
	{
		alert('You must donate at least 1 dollar per song');
		return false;
	}
	else
	{
		UpdatePaypalForm();
	}
}