The ComingSoon.net Box Office Report has been updated with studio estimates for the weekend. Be sure to check back on Monday for the final figures based on actual box office.

It was touch and go for a day or so, but according to estimates, Christopher Nolan’s The Dark Knight (Warner Bros.) has won the weekend, narrowly defeating the third installment of the “Mummy” franchise, The Mummy: Tomb of the Dragon Emperor (Universal) starring Brendan Fraser and Maria Bello.

Racking up its third weekend at #1, The Dark Knight added an estimated $43.8 million to its staggering $395 million take after just seventeen days, putting it in line to cross the $400 million mark tomorrow, the first movie to ever make that amount in just 18 days. (Shrek 2 was previously the fastest movie to hit $400 million, which it grossed in 43 days, so “Dark Knight” did the same two and a half times faster.) Currently, The Dark Knight is the eighth-highest grossing movie of all-time and Warner Bros.’ top grossing movie, but by this time next weekend, it’s likely to be the fifth or sixth highest grossing movie domestically as it starts targeting Star Wars Episode IV: A New Hope and E.T.: The Extra-Terrestrial. From there, it’s only $70 million away from becoming only the second movie in over 80 years of filmmaking to gross $500 million domestically, not accounting for inflation.

Internationally, The Dark Knight added $37 million for a total of $202.5 million overseas and a worldwide total of $597.5 million.

Directed by new helmer Rob Cohen, The Mummy: Tomb of the Dragon Emperor brought in an estimated $42.5 million in its opening weekend in 3,759 theaters, an average of $11,300 per site. To put those numbers in perspective, the third “Mummy” movie grossed less its opening weekend than the original movie in 1999, while The Dark Knight made more in its THIRD weekend than Tim Burton’s Batman made its opening weekend 19 years ago.

“Dragon Emperor” opened in first place internationally with $59.5 million at 3,559 theaters.

The Will Ferrell and John C. Reilly comedy Step Brothers (Sony) dropped 47% in its second weekend to bring in $16.3 million for third place with a gross of $63 million after ten days.

Universal Pictures’ musical Mamma Mia!, starring Meryl Streep and Pierce Brosnan, continues to do well, making $13.1 million in its third weekend, an insignificant drop of 26%, to bring its total to $88 million over a production budget of $52 million.

Brendan Fraser’s other big budget action/FX movie Journey to the Center of the Earth (New Line/Warner Bros.) dropped to fifth place with $6.9 million and a four-week gross of $73 million, putting it ahead of Guillermo del Toro’s Hellboy II: The Golden Army, which it opened against three weeks prior.

Kevin Costner’s political comedy Swing Vote (Touchstone Pictures) failed to find Costner’s regular audience, opening in sixth place with an estimated $6.3 million in 2,213 theatres, an average of just $2,847 per location. It is Costner’s weakest opening since The Postman over ten years ago.(Costner’s romantic comedy Rumor Has It with Jennifer Aniston opened on Christmas Sunday, giving it a single day opening weekend.)

On the other hand, Disney/Pixar’s WALL•E crossed the $200 million mark in its sixth weekend in theaters, adding another $4.5 million as it dropped one notch to eighth place.

At #7, Will Smith’s superhero flick Hancock brought in $5.2 million taking its own gross to $216 million.

The X-Files: I Want to Believe (20th Century Fox) plummeted 66%, dropping from #4 to #9 in its second weekend after an unimpressive opening gross. The Top 10 was rounded off by 20th Century Fox’s animated movie Space Chimps with $2.8 million bringing its total to $22.1 million.

After multiple delays, Lionsgate finally released the horror-thriller Midnight Meat Train in 102 cut-price theaters where it grossed just $32,000, averaging an awful $313 per venue, which probably would be expected considering the obvious dump of the movie.