If i am understanding you correctly, you want to put in flicker, not remove it?
Maybe you could use the sampleImage() command in an expression, to get some values out, from an scene sequence with some of the desired flicker.
Convert the expression to keyframes and, use these to drive an Exposure, or similar effect.
If you want to remove the flicker i can recommend the Flicker Free plugin, i have had good success with that so far.
Or the new revisionFX plugin DE:Flicker looks even more advanced and has some impressive demo footage