Loops

I normally am a bit lazy and using frames for tweening and aniamtion however I know I should use script ao I knocked to gether a loop that I thought would do that

on(press){
for (var b =_root.links._y; b>100;_root.links._y = b++){
trace(b);
}
}
this should make a movie clip move up the screen however it doesnt could someone put me straight