follow a leader with delay

hi

i have bunch of layers all distributed in z space.All in a row.So,they have all differenent position data.

Now the first layer starts to move towards the camera.After a specific time i.e 1.5 secs i want to move the second layer to move with the first one.etc.

thisComp.layer(thisLayer,-1).position.valueAtTime() doesn't work.

something similar to this>

start = 0; //start time of template motion
end = 4.0; //end time of template motion

t = thisComp.layer("template");
offset = (t.effect("offset")("Slider")/100)*(index -1);
travel = linear(t.effect("travel")("Slider")/100,start,end);
t.position.valueAtTime(travel - offset)

any ideas?

cheers