Lawyers for Viacom CEO Philippe Dauman and the company’s controlling shareholder Sumner Redstone will have to block out October 3-7 for a trial that could determine whether the Viacom chief remains a power within the Redstone media empire.

Massachusetts Probate and Family Court Judge George Phelan announced the dates for the showdown. Dauman and Viacom Director George Abrams want him to invalidate an effort by Redstone to replace them on his family trust and the board of National Amusements (NAI).

The seven-member trust will vote Redstone’s shares in the theater chain when he’s deemed unable to manage his affairs. That’s important: NAI owns 80% of the voting stock at Viacom and CBS.

Dauman and Abrams say that Redstone, 93, is already not capable of rational decision making, and being manipulated by his daughter, Shari, who’s Viacom’s Vice Chair. The plaintiffs want the court to order an independent examination of the elder Redstone.

The Redstones reject the charges, saying that Sumner is still calling the shots.

The trial is scheduled to begin on the first day of the Jewish new year, one of the faith’s most important holidays.