function validateQuantityField(fieldId, errorId)
{
	var s = $(fieldId).value.strip();
	var valid = false;
	
	var children = $(errorId).childNodes;
	for (var i = children.length - 1; i >= 0 ; i--)
	{
		$(errorId).removeChild(children[i]);
	}

	var res = s.match(/^(\d+)$/);
	if (res != null)
	{
		if (res.length > 0 && res[0] > 0)
		{
			valid = true;
		}
	}
	
	if (!valid)
	{
		$(errorId).appendChild(document.createTextNode('Please enter a valid quantity'));
	}
	
	return valid;
}