[Pierre-Marie Baty]

You can't change the amount of damage taken from the TraceLine that the bullet calls. You may be able to do it from a plugin by 1°) intercepting and changing on the fly all the "damage" network messages that the server sends and 2°) NOT FORGETTING to adapt the victim edict's health and armor on the server side too when you change one of them (but only after the messages are sent).