d56auction,
From reading other threads on this topic and recalling the Entertainment discount certificate from memory, it certainly seems that WBC bookings would be possible and a great discount.

Yet, I am in Taiwan now and don't have my entertainment number or book, so I can't see the exact rules but last month when I had to fly BOS FRA, I tried to use my Entertainment 15% discount. With WBC fares at $2100 or so, saving $300 seemed like a wonderful idea.

I tried to book online at www.nwa.com/entertainment and got the Gold Star (PD??? or PE???) discount for coach class, but when I tried WBC for the same itinerary, no discount showed, so I had to call NW. On the phone for nearly an hour as the agent tried and tried to make the discount work in WBC. We both kept reading the fineprint and said "Yeah the conditions are met" but it wouldn't book. Eventually she said "Ah here in the last paragraph it says "from Coach fares" or something similar (I dont have the certificate with me), and I couldn't book WBC.

Maybe others have. I would certainly like to use this discount in WBC (I could save $500 BOS TPE) and hope you get to do so.