I don't have AE right in front of me but you could always pre-compose your layer with the effect and then time reverse the layer.
Apply the transition to a solid on top of the layer and assign it as amtte for that layer. Also effects like Invert can simply invert the Alpha, but that may result in transparent areas outside the actual effect also becoming opaque.
Thank you for the reply.
I have already tried to do so but it does not work. The jaws move the same direction.
I will go through this process but I am afraid I have tried everything I could.
If I work out I will tell you.
Thank you so much for the answer.
I have to improve my knowledge of AE before getting the most of your suggestion.
I will get back to you if I cannot succeed.
You didn't move all attributes to the new composition. Try making a separate composition with just your jaws effect, drop that in your main comp and time reverse the nested comp. The motion in the frame has to reverse.
Thank you so much Rick for your help. I have not yet tried your advice. I am overworked now and I have to succeed another problem wich is more important (I will start a new discussion on that because I have not found out any answer for it).
I'll let you know as soon as I will resume this problem.