One Way Obsticales

[splashy5]

How would i make it so you can only go one way through a destructiable.
You go down a tree but you cant go back up it. But if you go around you can go back down it again.

 

[Wrel]

Could make it so you get to a certain point, and you get shoved down the direction, through a pathing blocker via triggers. That way the person would have to go around the pathing blocker to get to the point of pushyness.

 

[toofless]

you could make regions before, during and after the place then check which region the unit is in when it enters the middle region. if it's the lower region simply move the unit outside the region.