RandyS
I can tell you how to do what you want much more simply.
1.) Create a group that includes all your trees
2.) Put a single strand effect on the group (can similarly be accomplished with morph, state, or curtain). Set it to:
Number Chases = 1
Chase Size = 60 (you can play with this one to get the "look" you want)
Cycles = 1
Chase Types = Left-Right
3d Fade = Yes (checkbox)
3.) Choose the color you want
4.) For the reverse chase, copy and paste this effect behind the first single strand effect, change Chase Types to Right-Left, and choose the second color you want.
If the chase timing doesn't work the way you expect it to, try changing the Render Style between DEFAULT, PER PREVIEW, and SINGLE LINE in the Layer Settings menu. One of those will work depending on your layout.
If you're doing this with A/C trees, you'll want to create a group for each color of trees and apply the Single Strand effect to the group of the color you want to chase. Then put the "reverse chase" single strand effect on the group of the second color
