In Castro v. Fowler Equipment Co. (1965) 233 Cal. App. 2d 416, the issue was whether a third party tortfeasor could defeat a portion of its liability by proving what future benefits the injured employee would receive. (Id. at pp. 418-419.) The court stated: "No rating having been made by the Industrial Accident Commission, it is impossible for any court to determine what that rating might be. The commission has exclusive jurisdiction to determine compensation even where a third party action is brought before jurisdiction of the commission has been invoked. . . .It would have been improper for the jury to have heard testimony and made a finding of fact as to what the Industrial Accident Commission might award the respondent in the event of a hearing. However, the appellant did receive a credit on the judgment for the exact amount which was paid by the State Compensation Insurance Fund." (Id. at p. 421.) The language in Castro demonstrates that a trial court should not permit juries to make a finding regarding workers' compensation benefits not yet determined by the WCAB.