Concurring with opinion.

I concur to the extent that, by adopting the Fifth District’s opinion in Department of Corrections, State of Florida v. Mattress, 686 So.2d 740, 741 (Fla. 5th DCA 1997), the relief available to Appellant, if any, “should be obtained through administrative channels and, if'necessary, by filing a petition for writ of mandamus naming DOC as the respondent.”

Appéllant challenges the denial of his postconviction motion filed pursuant to Florida Rule of Criminal Procedure 3.800(a). In his motion, Appellant argued that the trial court improperly authorized the Department of Corrections (“DOC”) to determine whether his gain-time should be forfeited after he was found in violation of his probation. He alleged that despite the fact that DOC did not have the authority to forfeit his gain-time based upon the date of his offense, it was nonetheless forfeited. The trial court summarily denied the mo-tion. We hereby, affirm, as this-claim is *956not cognizable pursuant to rule 3.800(a). See Dep’t of Corrections v. Mattress, 686 So.2d 740, 741 (Fla. 6th DCA 1997).

AFFIRMED.