Idiot? Stop an action!

All I’m trying to do is stop a particular action (the snowfall animation) at a particular frame while allowing other animations (traditional layered/tweened stuff) that are occuring in other layers to continue on…

example: the total movie is 1000 frames long. I want the one action (snowfall effect) that is in one layer to stop on frame 500 while allowing the rest of the movie to continue. I know it’s simple but I can’t find the answer anywhere! please help.

Thanks all!