[Plugin: WordPress Simple Paypal Shopping Cart] wordpress simple paypal shopping cart & custom f

hello guys
i”m trying to add the add to cart button using the custom fields, i”ve found an example
above the loop
<?php $price = get_post_meta( $post->ID, ‘price’, true ); ?>

the place where i want the add to cart button
<?php echo print_wp_cart_button_for_product($name, $price); ?>

well … it”s not working, it displays the add to cart button but, when i click on it, it adds a noname and noprice product to my shopping cart

and yes i”ve put on the custom field post name: price / value: 25
and same thing :((

can u pls help me ?

http://wordpress.org/extend/plugins/wordpress-simple-paypal-shopping-cart/