Forge 1.7.10 Level Update Event

I wanted to experiment a little bit with Events, and I thought it would be a good idea to create a sword that can deal the same damage points the player has as level. Like you mine some ores, get about 5 Lvls, then the sword damage will be 5. For that I wanted to use something like a Level Event that gets triggered when the level changes, so the sword damage will get updated too. But I couldn't find any Tutorial for a Level Event, no matters how hard I looked