You could try creating a parallel event with this script
const c1 = $gamePlayer, c2 = $gameMap.event(001); $gameMap.distance(c1.x, c1.y, c2.x, c2.y) < 1
Let's say the chest was event 001, this would allow the parallel event to determine when the character is within one space of chest. You could then turn on a switch to temporarily change the state of the chests passibility.
