It shouldn't be too hard if you want it to simply trace the players footsteps
add global variables, something like "lastGridX" and "lastGridY"
and in the events:
when a condition for moving the player to a new grid space is met,
set LastGridX/Y to it's current position, *before* moving the player to it's new space.
and then set the followers position to the grid space in the LastGridX/Y
There may be a simpler way though, if your game is turn-based for example you can, on the start of a turn just set the followers position to the players position before moving the player to his new spot.