Can I have a slider impact a timeline just at one point?

Question

I am using AE CS6, on an HP 820z, Win 7.
I would like to have a series of layer objects follow different paths to an end point where they line up horizontally curving back in space on the sides.
Here is a small example:
But at the end point, I'd like to be be able to use a slider to adjust the x, y, & z axis. For the z axis, I'd like the orb of each layer pairs to fall behind the one in front of it on the z plane.  I can't figure out how to write an expression for that. Also I'd like the y axis to follow a besier curve that extends symmetrically to the right and left of the comp mid point.
This is what I have to separate the x axis but I can't figure out how to connect the y axist to a besier curve or to make each layer pairs ahead of it.
jeff
[thisComp.layer("Trajectory").effect("X Offset")("Slider"),transform.position[1],transform.position[2]]

Answer 1

nothing happens with the slider values until you set keyframes. I'm not sure what is causing the problem. A screenshot of the project may help but you can simply add a value + to your expression so that you can keyframe position and then add to the position values with your expression controller.
Something like this:
x = effect("Slider Control x")("Slider");
y = effect("Slider Control y")("Slider");
z = effect("Slider Control z")("Slider");
value + [x, y, z]
If you need to control more than one layer with a single set of sliders or a 3 Point Control then just point the other animated layers to the layer containing the expression controls.