You ought to create different actions for each zone and refer them to a entity placed in WED or per ent_create.

Each action defines a zone, based on the entity-position. I would create some parameters to define the width and the height of a zone. Additional I would create some global variables, that save each zone you refer in WED.

I think you´ve create for each cloud an action. So you only have to add a request in your cloud-action. This request should compare the cloud-position for beeing in one of your zones. If it is so, you could change the behaviour of your cloud, maybee the speed or the rotation or the color or something else.

I hope I could help you a bit...

best regards
steev