ActionScript 2.0 :: Spin The Globe - Globe Cannot Play Backward ?

my boss gave me the difficult project. he wants me spin the globe.now i can spin the globe forward and backward. but has one error that the globe cannot play backward continuous when my mouse is move more than 1/2 of stage width.it's should be

forward :: frame 1, 2, 3, 4, ..., 24
backward :: frame 24, 23, 22, 21, ..., 1

no have error when play on frame 1 - frame 23

find the error when play frame 24

it is forward :: frame 1, 2, 3, 4, ..., 24 and not play backward and the problem can found when play until the last frame.here is code

Code:
stop();
//forward
MovieClip.prototype.playForward = function() {[code]........