Show if item in cart
I have set up a product table with 7 items. The customer can only add one of these at a time.
Items 1-4 allow the customer to buy optional extras to the base product (5-7 are the extras for people who never bought them initially).
I have set up a button on the cart summary page which opens a pop up window and allows the customer to add to cart.
However I would only like this button to display when Items 1-4 are in the cart. The unique column is 'ProductID'.
Is there a way to do this?