Trimark Holdings Inc. announced yesterday that it plans to repurchase up to 400,000 shares, or about 9% of its outstanding common stock, in the open market.The move was subject to the approval of the company’s five-member board of directors. The NASDAQ-listed stock is currently selling at $ 4.50 vs. a book value of $ 6, according to a company spokesman. The company earned $ 2.23 million in 1992, compared to $ 2.61 million in 1991 . These figures compare to earnings of $ 4.23 million in 1990, when the stock went public at $ 12.50. Trimark is the holding company for Trimark Pictures, which has recently distributed “Warlock,”"The Favor, The Watch and The Very Big Fish” and “Whore.” It has 4.5 million shares outstanding, the bulk of which are closely held by the company’s employees and its founders. Only about 1.2 million shares are particularly liquid in the public market, per a company spokesman. Its IBS/Trimark subsidiary, purchased for $ 1.6 million in late 1991, distributes TV programming internationally. The company is looking for a potential boost in its 1993 earnings from its slate of upcoming theatrical releases. These include the Nicolas Cage-Michael Biehn film “Deadfall”; “FIS,” based on a secret department at the Los Angeles Police Dept.; and a sequel to “Warlock,” Trimark’s most successful release to date.