Help animating glow

Hey guys!

I just recently started working in blender, and I came across an issue.
My model is done and now I want to animate a part of it, specifically, to make the shown object emit light.
I’ve set different mission strength on different keyframes, but when I play the animation, emission remains the same as I last put it throughout all frames.
Can anyone help me solve this issue? I worked on the project for a while and would hate to see it unfinished on this last step.
Everything here is done in blender render.