You can add a condition, something like this:
System->Compare two values-> Distance(player.x, player.y, enemy.x, enemy.y)<500
then move enemy towards the player.
It's not specific to 8Direction behavior. You can compare distance or angle between two objects and execute different actions.
Have you checked the Tutorials section and FAQ? I'm sure you can find many examples on how to do such things.
And here is someone else's game that uses similar mechanics - when player gets close to bees, they start moving towards him and attacking, but once they get too close, they stop. It's not a very good code, but it does what you want.
https://www.dropbox.com/s/tvibytynqy997 ... .capx?dl=0