With multiplex marquees displaying appealing attractions for every demographic group during the week between Christmas and New Year, the box office seemed on track to chalk up $500 million for the week, a record, analysts observed. (The previous record was set last year following the opening of The Dark Knight, when combined ticket sales reached $396.2 million.) Leading the field was Fox's Avatar , which added another $18.5 million to its domestic gross on Wednesday, bringing it to $268.9 million after 13 days. (Far more impressive, however, is the foreign gross, which stood at $525.3 million on Tuesday.) Another Fox film, Alvin and the Chipmunks The Squeakquel , was also packing theaters on Wednesday with $11.8 million to bring its eight-day total to $112 million. In addition, Warner's Sherlock Holmes produced solid sales of $9.75 million on Wednesday, bringing its six-day total to $93.6 million. Among the holiday moviegoers was President Obama and his family, who were invited to attend a private screening of Avatar at a theater near their rented home in Hawaii. Only four theaters in the entire state are equipped with digital projectors and all are located on the island of Oahu, where the president is staying.