customer set price for gift cards

I have a restaurant client who wants to sell gift cards online. Ideally, the customer should be able to declare any dollar amount ($20, $23, $37, whatever) and then have that item set to that price and added to a shopping cart. (The client has their own gift card system and will be loading each card with the corresponding amount before mailing it out.) Is there a way to do this (allow the customer to type in any dollar amount as the price) with HikaShop?