Adjustable Timeline Animation

I have a series of 100 png files that form an animation. I want to cycle through them like a sprite image (which I was able to accomplish on my Fitbit with js, so I'm convinced it could be possible in storyline)

Basically I want the same animation to adjust based on the timeline. I'm building it in the master slide but I can't figure out the var needed for the timeline duration. So I can do the math to have the image switch every xx seconds based on the individual length of the slide. I'm Javascript novice. 

I know I could essentially do this with multistage image or sprite image but it's the slide duration adjustment that I'm struggling with.

Can anyone provide some help?