function productSelectionCheckbox(productId) {
	productCheckbox = document.getElementById('products_selection_' + productId + '_checkbox');
	productQuantity = document.getElementById('products_selection_' + productId + '_quantity');
	if (productCheckbox.checked) {
		productQuantity.focus();
	} else {
		productQuantity.blur();
		productQuantity.value = '';
	}
}

function productSelectionQuantity(productId) {
	productCheckbox = document.getElementById('products_selection_' + productId + '_checkbox');
	productQuantity = document.getElementById('products_selection_' + productId + '_quantity');
	if (productQuantity.value > 0) {
		if (!productCheckbox.checked) {
			productCheckbox.checked = 'checked';
		}
	} else {
		if (productCheckbox.checked) {
			productCheckbox.checked = '';
		}
	}
}