LOS ANGELES - With four films opening nationwide Friday -- including one from teen idol Justin Bieber -- Valentine's Day weekend should help shake off the malaise that has gripped the box office this year.

Sony's Adam Sandler-Jennifer Aniston romantic comedy "Just Go With It" is widely expected to open north of $30 million (some observers put the figure closer to $35 million) and win the weekend crown. The movie should also see a spike Monday, since that's when Valentine's Day falls.

Paramount's "Justin Bieber: Never Say Never" is the big wild card. Forecasting services readily admit they have a hard time gauging this sort of fare targeted at young girls.

Part biography, part concert film, the 3D release should open in between "Hannah Montana/Miley Cyrus: Best of Both Worlds Concert Tour," which debuted to $31.1 million in 2008, and "Jonas Brothers: The 3D Concert Experience," which opened to a much softer $12.5 million.

One thing that could bite into "Never Say Never" is the new cartoon "Gnomeo & Juliet," featuring music by Elton John. The film is tracking well among parents, who may try to convince girls to see "Gnomeo" instead of "Never Say Never."

The fourth film opening Friday is Focus Features' swords-and-sandals epic "The Eagle," which should play heavily to men. Tracking suggests an opening of $6-9 million.

Kevin Macdonald directed Channing Tatum in an adaptation of Rosemary Sutcliff's 1954 historical book "The Eagle of the Ninth," about a young Roman officer's search for the truth about the disappearance of his father's legion in Britain.