no loop for part of the animation

One way you can achieve your desired result is to use a series of MovieClips. To play an animation without it looping, you can add this.stop() to the last frame of your MovieClip. If you don't want a MovieClip to loop, don't include this.stop() inside of your MovieClip.

If you use this design method, you will need a way of navigating from one MovieClip to another after the non-looping animation has finished (e.g. this.parent.gotoAndStop(2)).

any timeline can be controlled with code, either as3 or js.  

if that doesn't solve the problem, is that what you're trying to control and which language are you using?