MultilingualBasketDisplay readonly?

I am trying to set the basket display text for a new discount.
The do***entation says that Discount.MultilingualBasketDisplay 
'gets' or 'sets' the displayed text

However the syntax only shows get, and i get a read-only compiler error.

disc = 
(Microsoft.CommerceServer.Marketing.Discount)marketingSystem.CampaignItems.NewDiscount(iCampaignId);
        LanguageStringCollection lsc ;
        lsc.Add(new LanguageString("Case Discount Applied!","en-US"));
        disc.MultilingualBasketDisplay= lsc;

How can i set the basket display for a new discount?

Thanks