Make a common event run "Parallel Process" on a switch that will always be on. In it, put an event line that is "Variable[XXX]=Hero's Level" (look for it). Then, put a small wait command of... 2 frames? 1 frame? That'll reduce a bit of lag sometimes.
Also, just reference to that variable you're using to do any events. Such as conditional branches. If Variable[XXX] = 3, then etc. Then it'll do the etc. if you're level 3.