Alternatively, you could put some code on the MC's 50th frame. Many coders like to keep their code on the main timeline, but this works too:
_root.gotoAndStop(5)
OR
_root.gotoAndPlay(5)
Depending on whether you want it to stop or play. Put that on the 50th frame (or whatever) of a Movie Clip, and when the Movie Clip reaches that frame, the main timeline will go to the 5th frame. Change the number in the brackets to change the frame.
The other suggestions work great too, but I felt like suggesting an alternative =)