My husband and I are US citizen going to Vietnam to visit. We have our passport and visa already. We would like to go from Vietnam to Shanghai(Tour)for a week sometimes in August and return to Vietnam for few days, and from Vietnam to Hongkong & Macau sometimes in August for few days. We're trying to get a friend to book the Tour in Vietnam in advance for me, however. Do we need to apply different China Visa or we can reuse the same China Visa to reenter to HongKong & Macau? We are unable to get the visa done in person thru the travel agency due to time restraint. Please help!!! Thanks.