Action on direction change

[isoetes]

Hello, I'm trying to program as follows:
Object A is controlled by the Player and the movement type is 'eight directions'.
Object B is not controlled by the Player and I want it to perform an action when object A changes direction of its movement.
I spent two evenings trying to figure it out but I just can't find the solution. Does anybody have any clue?
Thanks in advanse

[MuddyMole]

+ Direction of ObjA <> OldDirection(ObjA)
-> ObjA: Set OldDirection to Direction(ObjA)
-> ObjB: Do something...

[isoetes]

But how to select OldDirection parameter? When I type it to dialog box i get syntax error.

[MuddyMole]

It's just an alterable value - doesn't matter what you call it.