In that petition, the appellant challenged the legality of the life sentences imposed following his convictions for armed robbery and kidnapping with bodily injury. A petition for writ of mandamus is not the proper vehicle for obtaining post-appeal review of sentences imposed by a state court. "Mandamus is a remedy designed to compel the doing of ministerial acts[,]" Speedway Grading Corp. v. Barrow, 258 Ga. 693, 695 ( 373 S.E.2d 205) (1988), and will not lie when the act complained of involves the exercise of judicial discretion, such as sentencing ( Anderson v. McMurray, 217 Ga. 145 ( 121 S.E.2d 22) (1961); see also Guhl v. Crow, 237 Ga. 699 ( 229 S.E.2d 475) (1976)). In addition, "[m]andamus is not an appropriate remedy to compel the undoing of acts already done...." Speedway Grading, 258 Ga. at 695.