Stop eCart from incrementing items in cart
I need to stop users adding more than one of any item to the cart, usually through inattention. They wouldn't want to buy more than one of anything and I don't stock multiples anyway. So if ID already in cart session, quantity does not increment. No feedback to user is required, just no action.
I'm thinking it would go in the attached code segment, but I'm not sure how to craft the IF statement. Can anyone help?