The revolving door at Britney Spears's camp continues to spin: the singer is now in the process of replacing her latest attorney.

High-profile divorce lawyer Sorrell Trope, who has represented Nicole Kidman and Nicolas Cage, tells PEOPLE he'll soon work for Spears, 25, in her bitter custody dispute with Kevin Federline.

Trope will take over for Melvin Goldsman, who was named as Laura Wasser's replacement Monday after Wasser stepped down. Shortly after Wasser left, Spears's manager also quit.

"Yes, it's true Ms. Spears quit Melvin Goldsman's firm, but we haven't been officially retained yet," Trope says. "The paperwork has not been signed, and it has to have our firm's, Goldsman's and Ms. Spears's signatures. I anticipate it will be signed [Wednesday]."

The change in attorneys comes as Spears reels from her latest setback. On Tuesday a judge ruled in the custody case that the singer is a "habitual, frequent and continuous" user of alcohol and controlled substances. The judge ordered her to undergo twice-weekly random testing.

Los Angeles Superior Court Commissioner Scott Gordon also ruled that Spears must meet with a "parenting coach" at least twice a week for a total of eight hours, according to court documents released Tuesday. And both Spears and Federline, 29, were ordered to undergo joint co-parenting counseling and complete the Parenting Without Conflict program

Still, the judge maintained the current 50-50 custody arrangement, pending the outcome of independent evaluations of the children's circumstances. Court-appointed evaluators will spend time with the family and make recommendations to the judge in November.

"It would appear the court wanted to stabilize the status quo, but also implement orders that give as much protection to the kids until the court has the benefit of the ... evaluations," Federline's attorney, Mark Vincent Kaplan, tells PEOPLE.

Kaplan adds: "Kevin is happy the case is moving forward in a positive direction."