Hi,
there is no simple solution using Corona 9 or older. You would have to animate absorption color from the current value to plain white (or script it, or parameter-wire it depending on visibility of the parent…).
But Corona v10 will do that for you. Currently available as daily build. Changelog where it got implemented:
https://forum.corona-renderer.com/ Chaos Corona 10 for 3ds Max - Daily Builds Changelog #msg208744
Good Luck