Scale up only when marked

Hey there. In my project, I have coded my layers to be applied certain animations/effects only when there is a marker on the layer. The first marker being the start and the second being the end. (i.e change to color animation) However, I cannot find an animation that scales up the image then scales it down only DURING the selected period. I want it to scale up, let's say %3, then scale down to the original size. I think I can copy paste the same codes and it would work but I don't want to manually scale up via keyframes. Any way to help? 

(You can take this as an example: https://www.youtube.com/watch?v=BjHAZz3nT2o, the members' images scale up and down when they sing.)