How to make goto and Stop true/false?

In Flash MX I have a movie clip that is 32 frames long and loops. Now, what I want to happen is: when you press a button in the file, the movie clip will stop at frame 22. I don’t want it to “goto and stop”, instead, I want it to continue playing through until it hits 22.

i.e. if you hit the button at frame 5 it will continue playing until 22. or if you hit it at 27 it plays through the cycle, but stops at 22 (if possible, it would be great if I could get it to reverse if it was past 22, but i don’t want to be greedy).

Now, one way I thought of doing this was to have an "on open ‘stop at 22’ = false " and "on press button ‘stop at 22’ = true.

but now we come to my problem, I haven’t done scripting for the past several months, and obviously what I wrote above is not an accurate script, and I regretably have forgotten a lot of what I’ve learned, so if someone could help me get headed in the right direction again, I would really appreciate it.